JP7492990B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

The present invention relates to a plasma processing apparatus and a plasma processing method.

In the manufacture of semiconductor devices and flat panel displays (FPDs), plasma is used in etching and deposition processes. In these processes, it is known to use a plasma processing device equipped with an opposing electrode formed from a spiral antenna structure (Patent Document 1).

In these plasma processes, it is necessary to set and control the device configuration and processing conditions so that the spatial distribution of the generated plasma is in a specified state relative to the substrate being processed. For example, a plasma distribution (arrangement) state can be exemplified so that the in-plane distribution of the plasma processing on the substrate being processed is uniform.

In addition, in processes using such an apparatus, there are cases where different processes, such as an etching process and a deposition process, are performed in the same chamber, or where the same process is performed under different conditions, such as using different gas types, in the same chamber.
Even in this case, it is necessary to obtain a preferable plasma distribution (arrangement) in accordance with the processing content in each processing.

International Publication No. 2016/114232

However, an apparatus that can form a plasma distribution state that is preferable or required for a particular process does not necessarily form a plasma distribution state that is preferable or required for another process. In particular, in processes that use different gas species, even if a plasma distribution state that allows the required process to be performed with one gas species can be formed, a problem may arise in which a plasma distribution state that allows the required process to be performed with the other gas species cannot be formed at all, and no apparatus is known that can solve this problem.

Naturally, since different processes are performed on the same substrate in the same apparatus, it is required that the same processing conditions, such as in-plane uniformity, can be achieved in each process.
It is believed that such requirements can be met by changing and controlling the spatial distribution (arrangement) of the plasma in accordance with each process.
However, no devices or techniques are known that can change or set the spatial distribution (arrangement) of plasma to a degree that can be considered sufficient for each process, and there is a demand to make such processes possible.

Furthermore, even if it were possible to control the spatial plasma distribution (arrangement) as described above, there would be cases where the plasma conditions were insufficient, such as when the required electron density was not reached, and it could not be said that the required processing was possible.

The present invention has been made in consideration of the above circumstances, and aims to achieve the following objects.
1. The spatial distribution (arrangement) of the plasma must be able to be changed and set to a sufficient degree for each of the different processes.
2. To make it possible to simultaneously achieve the spatial distribution (arrangement) of plasma required for processing and the plasma conditions such as electron density required for processing.

(1) A plasma processing apparatus according to one aspect of the present invention includes:
A plasma processing apparatus comprising:
A chamber capable of reducing the pressure inside and configured to perform plasma processing on a workpiece inside the chamber;
a flat inner electrode disposed in the chamber and on which the workpiece is placed;
a spiral external electrode disposed outside the chamber and facing the internal electrode across a dielectric plate forming an upper lid of the chamber;
A plasma generating power source that applies AC power of a predetermined frequency to the external electrode;
a gas introduction means for introducing a process gas into the chamber;
Equipped with
the external electrode is divided in a radial direction to include a first spiral electrode arranged in a radial center portion, a second spiral electrode arranged in a radial outer periphery portion, and a third spiral electrode arranged and sandwiched between the first electrode and the second electrode in the radial direction,
The plasma generating power source is
a first high frequency power supply that applies AC power having a first frequency λ1 to the first electrode and the second electrode;
a second high frequency power supply that applies AC power of a second frequency λ2, the second frequency λ2 having a relationship of λ1>λ2 with the first frequency λ1 to the third electrode;
a power distributor that distributes power so that AC power distributed at a predetermined distribution ratio can be applied to the first electrode and the second electrode;
Equipped with
This has solved the above problem.
(2) The plasma processing apparatus of the present invention is the above-mentioned (1),
A plasma having a adjusted spatial distribution is generated by AC power of the first frequency λ1 distributed and applied to the first electrode and the second electrode, and an electron density of the plasma is increased by AC power of the second frequency λ2 applied to the third electrode.
be able to.
(3) The plasma processing apparatus of the present invention is the above-mentioned (1),
the power distributor is capable of distributing and applying a power at a predetermined distribution ratio such that a magnetic field distribution formed by the first electrode and the second electrode substantially coincides with a magnetic field distribution formed by the third electrode.
be able to.
(4) The plasma processing apparatus of the present invention is the above-mentioned (1),
The first high frequency power supply and the second high frequency power supply apply AC power having the first frequency λ1 of 13.56 MHz to the first electrode and the second electrode, and apply AC power having the second frequency λ2 of 2 MHz to the third electrode.
be able to.
(5) The plasma processing apparatus of the present invention is the above-mentioned (1),
The external electrode has portions stacked in the axial direction of the spiral.
be able to.
(6) The plasma processing method of the present invention is the above-mentioned (1),
A method for performing plasma processing using the plasma processing apparatus according to any one of (1) to (5) above,
A plasma is generated by the first electrode and the second electrode to which AC power of the first frequency λ1 is applied by the first high frequency power supply, and the AC power of the first frequency λ1 to be applied is distributed to the first electrode and the second electrode at a predetermined distribution ratio by the power distributor, thereby adjusting the spatial distribution of the generated plasma;
Increasing the electron density of the plasma by the third electrode to which AC power of the second frequency λ2 is applied by the second high frequency power supply;
be able to.
(7) The plasma processing method of the present invention is the above (6),
a distribution ratio of AC power applied to the first electrode and the second electrode by the power distributor is changed in response to the process gas introduced by the gas introduction means, thereby adjusting the spatial distribution of the generated plasma.
be able to.
(8) The plasma processing method of the present invention is the above (7),
The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.5:0.5 to 0.1:0.9
Set it to be in the range of
be able to.
(9) The plasma processing method of the present invention is the above (8),
The process gas is a film formation process using SiF ₄ /O ₂ gas;
be able to.
(10) The plasma processing method of the present invention is the above (6),
A distribution ratio of AC power Winner distributed to the first electrode and AC power Wouter distributed to the second electrode by the first high frequency power supply is
Winner:Wouter = 0.75:0.25 to 0.25:0.75
Set it to be in the range of
be able to.
(11) The plasma processing method of the present invention, in the above (10), further comprises:
The process gas is _{C4F8 gas} for film formation;
The process gas is SF ₆ /SiF ₄ /O ₂ gas etching process;
be able to.
(12) The plasma processing method of the present invention is the above (6),
The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.5:0.5 to 0.1:0.9
The process gas is set to be in the range of SiF ₄ /O ₂ gas for film formation,
The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.75:0.25 to 0.25:0.75
The process gas is set to be in the range of C ₄ F ₈ gas for film formation,
The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.75:0.25 to 0.25:0.75
The process gas is set to be in the range of SF ₆ /SiF ₄ /O ₂ gas for etching;
This is done continuously without breaking the vacuum.
be able to.

(1) A plasma processing apparatus according to one aspect of the present invention includes:
A plasma processing apparatus comprising:
A chamber capable of reducing the pressure inside and configured to perform plasma processing on a workpiece inside the chamber;
a flat inner electrode disposed in the chamber and on which the workpiece is placed;
a spiral external electrode disposed outside the chamber and facing the internal electrode across a dielectric plate forming an upper lid of the chamber;
A plasma generating power source that applies AC power of a predetermined frequency to the external electrode;
a gas introduction means for introducing a process gas into the chamber;
Equipped with
the external electrode is divided in a radial direction to include a first spiral electrode arranged in a radial center portion, a second spiral electrode arranged in a radial outer periphery portion, and a third spiral electrode arranged and sandwiched between the first electrode and the second electrode in the radial direction,
The plasma generating power source is
a first high frequency power supply that applies AC power having a first frequency λ1 to the first electrode and the second electrode;
a second high frequency power supply that applies AC power of a second frequency λ2, the second frequency λ2 having a relationship of λ1>λ2 with the first frequency λ1 to the third electrode;
a power distributor that distributes power so that AC power distributed at a predetermined distribution ratio can be applied to the first electrode and the second electrode;
Equipped with.

According to the above configuration, plasma is generated by AC power distributed and applied to the first electrode and the second electrode, and the electron density of the plasma is increased by AC power applied to the third electrode located between them, making it possible to perform plasma processing with a high degree of dissociation of the process gas molecules.
Therefore, the power distributor can control the distribution of the plasma generated by the first and second electrodes in a predetermined spatial distribution, i.e., the distribution of the amount of plasma generated in the radial direction of the chamber corresponding to the range defined by the positions of the first and second electrodes in the radial direction of the chamber, and the distribution of the amount of plasma generated between the outer electrode and the inner electrode. At the same time, the third electrode can control the electron energy probability function to a predetermined state, i.e., heat the low electron density plasma that is spatially controlled. As a result, it is possible to generate plasma in which the plasma distribution and temperature are simultaneously controlled, and perform a predetermined plasma processing.
Here, the range defined by the position from the first electrode to the second electrode in the radial direction of the chamber can include the position from the first electrode to the second electrode in the radial direction, as well as the area inside the first electrode in the radial direction, and the area outside the second electrode in the radial direction.
Furthermore, between the outer electrode and the inner electrode may include the area within the chamber in a direction from the opposing outer electrode toward the inner electrode.

(2) The plasma processing apparatus of the present invention is the above-mentioned (1),
A plasma having an adjusted spatial distribution is generated by AC power of the first frequency λ1 distributed and applied to the first electrode and the second electrode, and the electron density of the plasma is increased by AC power of the second frequency λ2 applied to the third electrode.

According to the above configuration, the spatial region in which plasma is generated can be controlled by controlling the distribution ratio of the magnetic field distribution formed by the first and second electrodes using a power distributor that serves as an RF splitter. At the same time, the third electrode, to which AC power of a frequency that cannot generate plasma by itself is applied, can be configured to apply electron vibrations to the generated plasma, thereby increasing the electron density in the plasma.

(3) The plasma processing apparatus of the present invention is the above-mentioned (1) or (2),
The power distributor is capable of distributing and applying power at a predetermined distribution ratio so that a magnetic field distribution formed by the first electrode and the second electrode substantially coincides with a magnetic field distribution formed by the third electrode.

According to the above configuration, by controlling the distribution ratio of the AC power applied to the first electrode and the second electrode with the power distributor, it is possible to control the arrangement state of plasma generation between the first electrode and the second electrode, that is, not only in the radial position of the chamber but also in the axial position of the external electrode. Here, the axial direction of the external electrode refers to the direction along the central symmetric axis when the helical shape of the helical external electrode is approximated by concentric multiple circles. In other words, the axial direction of the external electrode refers to the direction along the central axis of the chamber in the height direction, that is, the central axis in the opposing direction between the external electrode and the internal electrode.

(4) The plasma processing apparatus of the present invention is any one of the above (1) to (3),
The first high frequency power supply and the second high frequency power supply apply AC power having the first frequency λ1 of 13.56 MHz to the first electrode and the second electrode, and apply AC power having the second frequency λ2 of 2 MHz to the third electrode.

According to the above configuration, plasma can be generated and a plasma generation region (plasma generation area) can be set using 13.56 MHz AC power, and electron density can be increased using 2 MHz AC power.

(5) The plasma processing apparatus of the present invention is any one of the above (1) to (4),
The outer electrode has portions stacked in the axial direction of the spiral.

According to the above configuration, by configuring any one of the first electrode, second electrode, and third electrode to be stacked in multiple stages, the magnetic field strength formed by the electrodes arranged in multiple stages can be increased. This makes it easy to appropriately control the spatial distribution of the magnetic field strength according to the processing content performed by the plasma processing apparatus. Note that here, any one or more of the first electrode, second electrode, and third electrode can be selected to form multiple stages, or any one or more of the first electrode, second electrode, and third electrode can be selected to form a portion of the multiple stages.

(6) A plasma processing method according to another aspect of the present invention includes:
A method for performing plasma processing using the plasma processing apparatus according to any one of (1) to (5) above,
A plasma is generated by the first electrode and the second electrode to which AC power of the first frequency λ1 is applied by the first high frequency power supply, and the AC power of the first frequency λ1 to be applied is distributed to the first electrode and the second electrode at a predetermined distribution ratio by the power distributor, thereby adjusting the spatial distribution of the generated plasma;
The electron density of the plasma is increased by the third electrode to which AC power of the second frequency λ2 is applied by the second high frequency power supply.

According to the above configuration, by adjusting the distribution ratio by the power distributor, plasma can be generated to have a predetermined spatial distribution, and at the same time, the electron density of the plasma can be increased. Therefore, it is possible to realize in the same chamber the generation of plasma corresponding to different plasma arrangements depending on the process gas supplied, etc. At the same time, it is possible to generate plasma corresponding to different electron densities depending on the process gas supplied and the plasma processing performed on the workpiece. As a result, by simply controlling the AC power applied from the first high frequency power supply and the second high frequency power supply and the gas supplied, it is possible to perform plasma processing using different gas species or plasma processing under different conditions on the same workpiece using the same apparatus, and moreover, continuously, without the need to replace the apparatus configuration.
This makes it possible to carry out a plurality of processes while maintaining a desirable distribution of plasma processing, for example, in-plane uniformity of the processing surface, in substrate processing requiring a multi-stage process or the like.

(7) The plasma processing method of the present invention is the above (6),
The spatial distribution of the generated plasma is adjusted by changing the distribution ratio of the AC power applied to the first electrode and the second electrode by the power distributor in accordance with the process gas introduced by the gas introduction means.

According to the above configuration, by controlling the distribution ratio of the AC power applied to the first electrode and the second electrode, it is possible to control the arrangement state of plasma generation between the first electrode and the second electrode, that is, the range defined by the position from the first electrode to the second electrode in the radial direction of the chamber, the position from the first electrode to the second electrode in the radial direction, and the region inside the first electrode in the radial direction and the region outside the second electrode in the radial direction along the radial direction of the chamber.
Moreover, for a plurality of gases that behave differently in reactivity in plasma processing, it is possible to form a magnetic field strength having a spatial distribution corresponding to each gas. As a result, even if the spatial distribution of the magnetic field strength required differs depending on the different gas species, it is possible to form a magnetic field strength having a different spatial distribution corresponding to each gas species, thereby realizing the in-plane distribution of the required processing characteristics.

(8) The plasma processing method of the present invention is the above (6) or (7),
The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.5:0.5 to 0.1:0.9
Set the range to be:

According to the above configuration, in accordance with the range of the distribution ratio described above, the magnetic field strength on the radially outer side of the chamber is increased more than the magnetic field strength on the radially inner side of the chamber, thereby increasing the density of plasma generated near the radial outer edge of the chamber more than the density of plasma generated near the radial center of the chamber.
This makes it possible to take measures such as making the film thickness uniform in the radial direction of the substrate in cases where, for example, a gas is used whose processing characteristics are smaller at the outer periphery of the substrate than at the center of the substrate without power distribution, such as a gas whose film thickness is smaller at the outer periphery of the substrate than at the center of the substrate during a film formation process.

(9) The plasma processing method of the present invention is the above (8),
The process gas is SiF ₄ /O ₂ gas for the film formation process.

According to the above configuration, when a film containing silicon is formed by CVD, it is possible to improve the uniformity of the film thickness in the radial direction of the substrate.
Alternatively, even in the case of a gas in which the electron density is not higher at the outer periphery of the chamber than at the radial center of the chamber, or in the case of a gas that is more difficult to dissociate at the outer periphery of the chamber than at the radial center of the chamber, it is possible to improve the uniformity of the processing characteristics in the substrate radial direction.

(10) The plasma processing method of the present invention is the above (6) or (7),
A distribution ratio of AC power Winner distributed to the first electrode and AC power Wouter distributed to the second electrode by the first high frequency power supply is
Winner:Wouter = 0.75:0.25 to 0.25:0.75
Set the range to be:

According to the above configuration, in accordance with the range of the distribution ratio described above, the density of plasma generated near the radial center of the chamber and the density of plasma generated near the radial outer edge of the chamber can be balanced or tilted at a predetermined distribution ratio, from the case where the magnetic field strength on the radially outer side of the chamber is increased more than the magnetic field strength on the radially inner side of the chamber, to the case where the magnetic field strength on the radially outer side of the chamber is decreased more than the magnetic field strength on the radially inner side of the chamber.
This makes it possible to take measures such as making the film thickness uniform in the radial direction of the substrate in cases where, for example, power distribution is not performed and a gas is used that causes variations in processing characteristics between the outer periphery of the substrate and the center of the substrate, such as a gas that causes variations in film thickness between the center of the substrate and the outer periphery of the substrate in a film formation process.

(11) The plasma processing method of the present invention, in the above (10), further comprises:
The process gas is _{C4F8 gas} for film formation;
The process gas is SF ₆ /SiF ₄ /O ₂ gas for etching treatment.

With the above configuration, it is possible to take measures such as making the processing characteristics uniform in the radial direction of the substrate in a process in which the processing characteristics at the outer periphery of the substrate and the processing characteristics at the center of the substrate vary when power distribution is not performed. For example, as described above, it is possible to improve the uniformity of the in-plane distribution of the etching depth in an etching process, the amount removed by an ashing process, the film thickness in a film formation process, and the like.

(12) The plasma processing method of the present invention is the above (6) or (7),
The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.5:0.5 to 0.1:0.9
The process gas is set to be in the range of SiF ₄ /O ₂ gas for film formation,
The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.75:0.25 to 0.25:0.75
The process gas is set to be in the range of C ₄ F ₈ gas for film formation,
The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.75:0.25 to 0.25:0.75
The process gas is set to be in the range of SF ₆ /SiF ₄ /O ₂ gas for etching;
This is continued without breaking the vacuum.

According to the above configuration, when multi-stage processing is performed in the same chamber while maintaining the sealed state of the chamber, these processing steps can be performed continuously while maintaining the in-plane uniformity of the processing characteristics in each processing step.
The present invention can be applied to an etching method for etching a workpiece, the method comprising: a resist pattern forming step of forming a resist layer having a pattern made of resin on the workpiece; an etching step of etching the workpiece on which the resist pattern has been formed; and a resist protective film forming step of forming a resist protective film on the resist pattern, the method including inserting the resist protective film forming step at a predetermined frequency into the etching step which is repeated a plurality of times.

The present invention makes it possible to provide a plasma processing apparatus and a plasma processing method that can change and set the spatial distribution (arrangement) of plasma to a sufficient degree even for different processes, and can achieve both the spatial distribution (arrangement) of plasma required for the process and the plasma conditions such as electron density required for the process.

1 is a schematic cross-sectional view showing a first embodiment of a plasma processing apparatus according to the present invention; 2 is a schematic perspective view showing an external electrode and other components in the first embodiment of the plasma processing apparatus according to the present invention; FIG. 1 is a schematic cross-sectional view illustrating plasma generation in a first embodiment of a plasma processing method according to the present invention. 1 is a schematic cross-sectional view illustrating plasma generation in a first embodiment of a plasma processing method according to the present invention. 1 is a flowchart showing a plasma processing using a first embodiment of a plasma processing method according to the present invention. 1A to 1C are cross-sectional views showing process steps of a plasma processing method according to a first embodiment of the present invention. 1A to 1C are cross-sectional views showing process steps of a plasma processing method according to a first embodiment of the present invention. 1A to 1C are cross-sectional views showing process steps of a plasma processing method according to a first embodiment of the present invention. 1A to 1C are cross-sectional views showing process steps of a plasma processing method according to a first embodiment of the present invention. 1A to 1C are cross-sectional views showing process steps of cycle etching in an embodiment of a plasma processing method according to the present invention. 1A to 1C are cross-sectional views showing process steps of cycle etching in an embodiment of a plasma processing method according to the present invention. 1A to 1C are cross-sectional views showing process steps of cycle etching in an embodiment of a plasma processing method according to the present invention. 1A to 1C are cross-sectional views showing process steps of cycle etching in an embodiment of a plasma processing method according to the present invention. 1A to 1C are cross-sectional views showing process steps of cycle etching in an embodiment of a plasma processing method according to the present invention. 1A to 1C are cross-sectional views showing process steps of cycle etching in an embodiment of a plasma processing method according to the present invention. 1A to 1C are cross-sectional views showing process steps of cycle etching in an embodiment of a plasma processing method according to the present invention. 1A to 1C are cross-sectional views showing process steps of cycle etching in an embodiment of a plasma processing method according to the present invention. 11 is a graph showing a change in film thickness due to splitting in an embodiment of the plasma processing method according to the present invention. 11 is a graph showing a change in film thickness due to splitting in an embodiment of the plasma processing method according to the present invention. 11 is a graph showing a change in film thickness due to splitting in an embodiment of the plasma processing method according to the present invention. 11 is a graph showing a change in film thickness due to splitting in an embodiment of the plasma processing method according to the present invention. 11 is a graph showing a change in film thickness due to splitting in an embodiment of the plasma processing method according to the present invention. 4 is a graph showing a change in film thickness in an example of a plasma processing method according to the present invention. 4 is a graph showing a change in film thickness in an example of a plasma processing method according to the present invention. 11 is a graph showing a change in etching due to splitting in an embodiment of the plasma processing method according to the present invention. 4 is a graph showing a change in etching depth due to frequency superposition in an embodiment of the plasma processing method according to the present invention. 11 is a graph showing a change in etching depth depending on whether or not frequency superposition is performed in an embodiment of the plasma processing method according to the present invention. 10 is a graph showing a change in deposition film thickness depending on whether or not frequency superposition is performed in an embodiment of the plasma processing method according to the present invention. FIG. 2 is a diagram showing a magnetic field strength distribution in a plasma processing apparatus. FIG. 2 is a diagram showing a magnetic field strength distribution in a plasma processing apparatus. FIG. 4 is a diagram showing a magnetic field strength distribution in an embodiment of the plasma processing apparatus according to the present invention. FIG. 4 is a diagram showing a magnetic field strength distribution in an embodiment of the plasma processing apparatus according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a plasma processing apparatus and a plasma processing method according to the present invention will be described below with reference to the drawings.
Fig. 1 is a schematic cross-sectional view showing a plasma processing apparatus according to this embodiment. Fig. 2 is a schematic perspective view showing an external electrode and a power supply of the plasma processing apparatus according to this embodiment. Fig. 2 shows the position where two spiral electrodes are arranged at the center and outer periphery on the radially inner side of the apparatus shown in Fig. 1, and a third spiral electrode is further arranged between them in the radial direction, and the power supply is connected to each of these three electrodes. In the figure, reference numeral 10 denotes the plasma processing apparatus.

As shown in Figures 1 and 2, the plasma processing apparatus 10 according to this embodiment is an apparatus that performs plasma processing on a workpiece (silicon substrate) S in a chamber 11 that can be depressurized by, for example, an exhaust means (depressurization means) TMP.

The plasma processing apparatus 10 includes a sealable chamber 11, a flat internal electrode (substrate support means) 12, a top cover 13, a spiral first electrode E1 (antenna AT1), a spiral second electrode E2 (antenna AT2), a spiral third electrode E3 (antenna AT3), a gas inlet 14, a gas inlet 15, a gas inlet means (not shown), a power distributor 16, a high-frequency power source (plasma generation power source) 17, a high-frequency power source (plasma heating power source) 18, and a high-frequency power source (bias power source) 19. Note that the term "spiral" here includes a concentric circular shape with only one turn.

The internal electrode (support means) 12 is disposed in the chamber 11, and supports the object to be processed S. The high frequency power supply (third high frequency power supply) 19 is capable of applying a bias power of a frequency (third frequency) λ3 to the internal electrode 12.
The first spiral electrode E1 (external electrode; antenna AT1), the second spiral electrode E2 (external electrode; antenna AT2), and the third spiral electrode E3 (external electrode; antenna AT3) are all arranged outside the chamber 11.

The first spiral electrode E1, the second spiral electrode E2, and the third spiral electrode E3 are disposed opposite the internal electrode 12, sandwiching a dielectric plate such as quartz that forms the top lid 13 of the chamber 11. The first spiral electrode E1 is disposed in the center along the top lid 13, and the second spiral electrode E2 is disposed on the outer periphery of the second electrode E2 along the top lid 13. The third spiral electrode E3 is disposed in a position between the first spiral electrode E1 and the second spiral electrode E2 in the radial direction of the chamber 11.
In the plasma processing apparatus 10 , a gas introducing means 100 is connected to a chamber 11 .

In the plasma processing apparatus 10, the same frequency λ1 is applied to the first electrode E1 and the second electrode E2. Compared to the frequency λ1 applied to the first electrode E1 and the second electrode E2, the frequency λ2 applied to the third electrode E3 is set to be lower. The first electrode E1 and the second electrode E2 are the electrodes that apply the higher frequency λ1, and the third electrode E3 is the electrode that applies the lower frequency λ2. In other words, in the plasma processing apparatus 10, the first frequency λ1 and the second frequency λ2 have a relationship of λ1 > λ2.

The high frequency power supply (first high frequency power supply) 17 can apply AC power of frequency (first frequency) λ1 to the first electrode E1 and the second electrode E2 (FIG. 1). The first electrode E1 has a first portion disposed at the inner peripheral end of the spiral and to which high frequency power is applied from the first high frequency power supply 17, and a second portion disposed at the outer peripheral end of the spiral and grounded to earth (FIG. 2). The first portion is close to the radial center of the chamber 11. The second portion is close to the third electrode E3.

The second electrode E2 has a third portion disposed at the inner peripheral end of the spiral and to which high frequency power is applied from the first high frequency power source 17, and a fourth portion disposed at the outer peripheral end of the spiral and grounded to earth (FIG. 2). The third portion is adjacent to the third electrode E3. The fourth portion is adjacent to the outermost circumference in the radial direction of the chamber 11.

The high frequency power supply (second high frequency power supply) 18 can apply AC power of frequency (second frequency) λ2 to the third electrode E3 (FIG. 1). The third electrode E3 has a fifth portion located at the inner peripheral end of the spiral and to which high frequency power is applied from the second high frequency power supply 18, and a sixth portion located at the outer peripheral end of the spiral and grounded to earth (FIG. 2). The fifth portion is adjacent to the first electrode E1. The sixth portion is adjacent to the second electrode E2.

The first high frequency power supply 17 applies AC power of a first frequency λ1 to the first electrode E1 and the second electrode E2 via the power distributor 16. The power distributor 16 is connected to the first high frequency power supply 17 and is capable of setting the distribution ratio of the AC power applied to the first electrode E1 and the second electrode E2. The power distributor 16 includes a variable capacitor or the like and is configured to be capable of setting the distribution ratio of the power to be supplied.
The second high frequency power supply 18 applies AC power of a second frequency λ2 to the third electrode E3.

In the plasma processing apparatus 10, the gas introduction means 100 is connected to the center of the top lid 13 or to the sidewall of the chamber 11 (FIG. 1). The gas introduction means 100 in the plasma processing apparatus 10 introduces a predetermined process gas G into the chamber 11 from a gas introduction port 14 arranged on the sidewall of the chamber 11 or a gas introduction port 15 arranged in the center of the top lid 13. The gas introduction means 100 can switch between different types of process gas G to be introduced into the chamber 11 depending on the process. The gas introduction means 100 can also supply a single type of gas or a mixture of multiple types of gas at a predetermined flow rate ratio as the process gas G to be introduced into the chamber 11.

Here, the gas introduction means 100 can supply different gases as the process gas G to be introduced into the chamber 11 in response to different plasma processes. The choice between gas introduction port 14 and gas introduction port 15 can be determined based on the characteristics of the gas to be supplied, the characteristics in plasma generation, the spatial distribution of the plasma, the processing characteristics of film formation, etc. Furthermore, gas can be supplied from both gas introduction port 14 and gas introduction port 15, and the distribution ratio, composition ratio, etc. can also be controlled to be adjusted.

The plasma processing apparatus 10 has a solid source 20 for sputtering in the chamber 11, on the side of the top lid 13 of the chamber 11 and in a position facing the internal electrode 12. In particular, in the plasma processing apparatus 10, the area in which the solid source 20 is arranged is provided in a position overlapping with the second electrode E2 arranged on the outer periphery.

In the plasma processing apparatus 10, the region in the chamber 11 where the solid source 20a is arranged is located at a position that overlaps with the first electrode E1, the third electrode E3, and the second electrode E2, and is arranged so as to cover the internal electrode 12. The solid source 20a is provided separately from the top lid 13 of the chamber 11.

When the process gas is supplied from the gas introduction means 100 into the chamber 11 in this embodiment, the pressure inside the chamber 11 can be reduced by the pressure reduction means TMP. The pressure reduction means TMP can also be used to evacuate the chamber 11.

In plasma processing in the plasma processing apparatus 10 , a predetermined process gas G is introduced into the chamber 11 from the gas inlet 15 by the gas introduction means 100 .
In the plasma processing apparatus 10, the first electrode E1 and the second electrode E2 generate a magnetic field in which a formation region is defined on the side of the upper lid 13 in the chamber 11, and generate a magnetic field with a regulated spatial distribution in the chamber 11. In addition, the third electrode E3 generates a magnetic field capable of heating the plasma P and increasing the electron density.
The magnetic fields generated by the first electrode E1, the second electrode E2, and the third electrode E3 using powers of different frequencies are superimposed on each other.

In the plasma processing apparatus 10, the magnetic field formed by the first electrode E1 and the second electrode E2 defines a formation region on the top lid 13 side in the chamber 11, and generates plasma P with a regulated spatial distribution in the chamber 11. In addition, the magnetic field formed by the third electrode E3 heats the plasma P, increasing the electron density.

In the plasma processing in the plasma processing apparatus 10, AC power of a first frequency λ1 is applied to the first electrode E1 and the second electrode E2 by the first high frequency power supply 17. As a result, a plasma P is generated in the chamber 11.
When the first high frequency power supply 17 outputs high frequency power, the high frequency power of the first frequency λ1 output from the first high frequency power supply 17 is simultaneously supplied to a parallel circuit consisting of the first electrode E1 and the second electrode E2, which are two antennas. At this time, the antenna matching box M/B matches the output impedance of the first electrode E1 with the input impedance of the load including the second electrode E2 by the first matching circuit.

Furthermore, the output impedance of the first high frequency power supply 17 is matched with the input impedance of the load including the first electrode E1 and the second electrode E2 by the matching circuit of the antenna matching box M/B.
At the same time, the output variable capacitor of the power distributor 16 sets the amount of current flowing to the first electrode E1 side and the amount of current flowing to the second electrode E2 side as a predetermined distribution ratio.

At this time, by setting the distribution ratio of the AC power applied from the first high frequency power supply 17 to the first electrode E1 and the second electrode E2, it is possible to set the region where the plasma P is generated and its spatial distribution.
Here, the power distributor 16 can set the spatial distribution of the magnetic field formed by the first electrode E1 and the second electrode E2 to coincide with the spatial function of the magnetic field formed by the third electrode E3. Alternatively, the power distributor 16 can control the superposition state of the magnetic fields with different frequencies according to the characteristic distribution required for the plasma processing performed by the generated plasma P.

FIG. 3 is a schematic cross-sectional view illustrating plasma generation in the plasma processing method according to the present embodiment.
Specifically, as shown in Fig. 3, when the power distributor 16 applies a larger AC power of the first frequency λ1 to the first electrode E1 than to the second electrode E2 as a distribution ratio of the AC power applied from the first high frequency power supply 17 to the first electrode E1 and the second electrode E2, the intensity of the plasma P generated in the space below the first electrode E1 becomes stronger than that of the space below the second electrode E2. This state is indicated by P1 in Fig. 3. In other words, the plasma P1 is generated mainly on the outer periphery side in the radial direction of the chamber 11.
Here, the intensity of the generated plasma P becomes stronger means that the density of the plasma P increases and/or the area in which the plasma P is generated becomes larger.

In contrast, as shown in FIG. 3, when the power distributor 16 applies a larger AC power of the first frequency λ1 to the second electrode E2 than to the first electrode E1 as a distribution ratio of the AC power applied from the first high frequency power supply 17 to the first electrode E1 and the second electrode E2, the intensity of the plasma P generated in the space below the second electrode E2 becomes stronger than that in the space below the first electrode E1. This state is indicated by P2 in FIG. 3. In other words, the plasma P2 is generated mainly in the center of the chamber 11 in the radial direction.

Furthermore, as shown in FIG. 3, when the power distributor 16 distributes the AC power of the first frequency λ1 applied to the first electrode E1 and the second electrode E2 from the first high frequency power supply 17 approximately evenly as a distribution ratio of the AC power applied to the first electrode E1 and the second electrode E2, the plasma P generated in the space below the first electrode E1 and the space below the second electrode E2 is distributed approximately evenly. This state is indicated by P3 in FIG. 3. In other words, the plasma P3 is generated approximately evenly in the radial direction of the chamber 11.

Here, the generation area of the plasma P is not set only by the distribution ratio of the AC power applied to the first electrode E1 and the second electrode E2 by the power distributor 16, but its spatial distribution also changes depending on the process gas G being supplied.
This is because gas properties such as the ease of ionization of the gas vary depending on the type of gas in the process gas G and its mixing ratio.

For example, even if the power distributor 16 applies the same AC power distribution ratio to the first electrode E1 and the second electrode E2, if the gas has characteristics such as the electron density not increasing on the outer periphery compared to the radial center, or being difficult to dissociate, the plasma will be more likely to be generated in the radial center of the chamber 11, like plasma P2.

In addition, even if the power distributor 16 applies the same AC power distribution ratio to the first electrode E1 and the second electrode E2, if the gas has characteristics such as the electron density not increasing more toward the center than the radial outer periphery, or being difficult to dissociate, plasma P3 will be more likely to be generated on the radial outer periphery of the chamber 11.

In other words, even if the tendency of the area where plasma P is generated varies depending on the type and supply state of the process gas supplied, including the surrounding area in the direction sandwiched between the first electrode E1 and the second electrode E2, the power distributor 16, as a so-called RF splitter, sets the distribution ratio of the AC power applied from the first high-frequency power supply 17 to the first electrode E1 and the second electrode E2, making it possible to control the variation in the area where plasma P is generated and the variation in the spatial distribution of the plasma intensity.

Furthermore, in the plasma processing in the plasma processing apparatus 10, as described above, the power distributor 16 sets the distribution ratio of the AC power applied from the first high frequency power supply 17 to the first electrode E1 and the second electrode E2, thereby setting the spatial distribution of the plasma P to a predetermined state, and then the second high frequency power supply 18 applies AC power of the second frequency λ2 to the third electrode E3. This increases the electron density of the plasma P, and the third electrode E3 to which AC power of the second frequency λ2, which cannot generate plasma by itself, is applied is configured to be able to apply electron vibrations to the generated plasma P, thereby increasing the temperature state in the plasma and setting the processing characteristics such as reactivity in the plasma processing to the required state.

FIG. 4 is a schematic cross-sectional view illustrating plasma generation in the plasma processing method according to the present embodiment.
Specifically, as shown by PP in FIG. 4, AC power of the second frequency λ2 is applied to the third electrode E3 by the second high frequency power supply 18, thereby further heating the generated plasma P and increasing the electron density of the plasma.
This makes it possible to perform sufficient processing even when using a process gas having characteristics such as a process gas that does not increase the electron density on the outer periphery side of the radial center of the chamber and is difficult to dissociate.
Furthermore, since the power distributor 16 sets the distribution ratio of the AC power applied from the first high frequency power supply 17 to the first electrode E1 and the second electrode E2, thereby setting the spatial distribution in which the plasma P is generated to a predetermined state, it becomes possible to set only the electron density independently.

Furthermore, the plasma processing apparatus 10 in this embodiment can be used as a plasma processing method for a process in which a plurality of plasma processing steps are successively performed on the substrate S, such as a dry etching process and the associated deposition (film formation) process, an ashing process, and an etching process performed following the film formation process, using a glass substrate, a quartz substrate, a silicon substrate, a silicide substrate such as a MoSi substrate or a SiC substrate, or a resin substrate as the substrate S.

Specifically, examples of such processes _{include a dry etching process for etching a silicon substrate using a fluorine compound, an anisotropic plasma treatment using a perfluorohydrocarbon gas such as CHF3, C2F6, C2F4, or C4F8 as a deposition process ,} an ashing process in which _O2 gas is supplied, and a process in which _SF6 or _NF3 is used as an etching gas, _SiF4 is added to the etching gas as a silicon compound, and _O2 , _N2 , _N2O , NO, _NOx , or _CO2 is added to the etching gas to intensively etch the bottom of a hole, etc.

In addition, when performing processes in succession that make it difficult to maintain in-plane uniformity in terms of etching depth and respective film formation rates, such as processes in which an etching process and multiple film formation stages using different gas types are performed continuously or intermittently, the distribution ratio of the AC power applied to the first electrode E1 and the second electrode E2 by the power distributor 16 can be changed in response to the supplied gas so as to uniformize the in-plane distribution of the processing characteristics, thereby achieving processing uniformity along the substrate processing surface.

Furthermore, in continuous or intermittent multi-stage plasma processing in which different gas species are supplied, the plasma temperature may be controlled by varying the AC power applied to the third electrode E3 to achieve uniformity of processing characteristics along the substrate processing surface.

For example, the first frequency λ1 of the AC power applied to the first electrode E1 and the second electrode E2 by the first high frequency power supply 17 can be set to a range of 10 MHz to 100 MHz, particularly 13.56 MHz. This makes it possible to ignite plasma in the process gas G supplied into the chamber 11, and to set the plasma state, such as the spatial distribution region where the plasma P is generated. This makes the AC power of the first frequency λ1 the power for generating plasma.
Moreover, the second frequency λ2 of the AC power applied to the third electrode E3 by the second high frequency power supply 18 can be set to a range of 0.1 MHz to 10 MHz, and particularly 2 MHz, which enables further excitation of the plasma and increases the electron energy probability function to increase the electron density.

In this manner, when performing a number of plasma processing steps, such as forming recesses in a silicon substrate by a method based on the so-called Bosch process, and further when these multiple steps are repeated as one cycle, it is possible to set the processing characteristics to a desired state, such as maintaining the in-plane uniformity of the plasma processing in each process, particularly when a different processing gas is used in each process.
Moreover, by individually setting the plasma temperature and plasma distribution in each process, it is possible to maintain a preferable processing state, such as depth penetration.

The following describes an embodiment of the present invention.

Here, a cycle process of silicon deposition and etching will be described as a specific example of a confirmation test of the plasma processing apparatus and plasma processing method of the present invention.
FIG. 5 is a flow chart showing an etching method as a cycle process in this embodiment.

The etching method according to this embodiment is a silicon dry etching method in which etching is performed while protecting a resist such as resin, using a silicon substrate S as the processing object. However, the etching method is not limited to this, as long as etching is performed while protecting the resist.

In the silicon dry etching method according to this embodiment, as shown in FIG. 5, a recess pattern VS and a recess pattern VL are formed on the surface of a silicon substrate S through a multi-cycle process (see FIGS. 6 to 11).
The recessed pattern VS has a diameter dimension ΦS. The recessed pattern VL has a diameter dimension ΦL. The diameter dimension ΦL may be set to be larger than the diameter dimension ΦS.

The recessed pattern VS and the recessed pattern VL are set to the same depth.
The recessed pattern VS and the recessed pattern VL are formed in a shape having a high aspect ratio of, for example, about 4 to 8, and more preferably, about 8 to 14.
The recess patterns VS and VL may penetrate the silicon substrate S.

As shown in FIG. 5, the silicon dry etching method according to this embodiment includes a pre-process S01, a resist pattern forming process S02, a deposition process S03, a dry etching process S04, an ashing process S05, a depth determination process S06a, a resist protection determination process S06, a resist protective film forming process S07, and a post-process S08.
6, a resist protective film forming step S07, and a post-process S08.

In the pre-processing step S01 shown in FIG. 5, the silicon substrate S is pre-processed by heat treatment at 200°C or higher using a known lamp heater or the like.

6A to 6C are cross-sectional views showing steps of the dry etching method for silicon in this embodiment.
In the resist pattern forming step S02 shown in FIG. 5, a resist layer (mask layer) M having a pattern is formed on the surface of a silicon substrate S as shown in FIG.
The resist layer (mask layer) M can be formed from a known resin resist. It can be formed to a predetermined thickness by appropriately selecting conditions such as positive type, negative type, exposure wavelength, coating method, film formation method, etc. Examples of materials constituting the resist layer (mask layer) M include photosensitive insulators and other known materials.

Furthermore, in the resist pattern formation process S02, as shown in FIG. 6, an opening pattern (mask pattern) MS that sets a processing area corresponding to the shape of the recess pattern VS in the silicon substrate S, and an opening pattern (mask pattern) ML that sets a processing area corresponding to the shape of the recess pattern VL are formed in the resist layer (mask layer) M.
Specifically, in the resist pattern formation process S02, a resist layer (mask layer) M which is a photoresist is laminated, and processing such as exposure and development is performed, and further, well-known processing such as wet etching processing and dry etching processing is performed to form a resist layer (mask layer) M having an opening pattern MS and an opening pattern ML.

7A to 7C are cross-sectional views showing steps of the dry etching method for silicon in this embodiment.
In the deposition process S03 shown in FIG. 5, a deposition layer D1 made of a polymer such as fluorocarbon is formed on the entire surface of the silicon substrate S by anisotropic plasma processing, as shown in FIG. 7, so that the side walls of the recess patterns VS and VL can be protected from etching in the dry etching process S04.

In the dry etching process S04, which is etching using a fluorine compound, the deposition layer D1 protects the side walls VSq, VLq of the recess patterns VS, VL from etching and limits the etching to the bottoms VSb, VLb of the recess patterns VS, VL in order to achieve vertical side walls VSq, VLq.

The deposition layer D1 is deposited on the surface of the resist layer (mask layer) M and on the bottoms VSb, VLb of the recess patterns VS, VL. In addition, although FIG. 7 shows the deposition layer D1 on the side walls VSq, VLq of the recess patterns VS, VL, in reality, it is not deposited very much.

In the deposition step S03, plasma processing is performed using a fluorocarbon gas such as CHF ₃ , C ₂ F ₆ , C ₂ F 4 or C ₄ F _8. As described above, the plasma processing apparatus 10 shown in FIGS.

In the deposition process S03, in the plasma processing apparatus 10, the frequency λ1 of the high frequency power applied to the first electrode E1 and the second electrode E2 can be set to be higher than the frequency λ3 of the high frequency power applied to the third electrode E3. Specifically, the frequency λ1 can be set to 13.65 MHz, and the frequency λ2 can be set to 2 MHz. In the deposition process S03, both the power of frequency λ1 and frequency λ2 can be set to the maximum value that the power sources 17 and 18 can output, thereby improving the rate.

In the deposition step S03, the AC power having a high frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to a value smaller than that in the dry etching step S04 and the ashing step S05 described later. In the plasma processing device 10, a bias voltage can be not applied to the internal electrode 12.
In the deposition step S03, the process is performed under a predetermined atmospheric pressure. Furthermore, in the deposition step S03, a predetermined amount of a rare gas such as Ar may be added.

In the deposition step S03, AC power having a frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This prevents the deposition rate of the deposition layer D1 from varying in the radial direction. The power distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in the deposition rate.

The deposition layer D1 formed in the deposition process S03 has a larger film thickness at the bottom VLb corresponding to the opening pattern ML with a larger diameter dimension than at the bottom VSb corresponding to the opening pattern MS with a smaller diameter dimension. The film thickness of the deposition layer D1 at the bottom VLb of the opening pattern ML is equal to or smaller than the film thickness of the deposition layer D1 on the surface of the resist layer (mask layer) M that is outside the opening patterns MS and ML.

In other words, the thickness of the deposition layer D1 decreases in the following order: thickness TD1 of the deposition layer D1 on the surface of the resist layer (mask layer) M outside the opening patterns MS, ML, thickness TLD1 of the deposition layer D1 at the bottom VLb of the opening pattern ML, and thickness TSD1 of the deposition layer D1 at the bottom VSb of the opening pattern MS.

In the deposition process S03, by setting the conditions as described above, it is possible to control the deposition coverage of the deposition layer D1 at the bottoms VSb and VLb corresponding to the opening patterns MS and ML so as to optimize them. Here, the direction of the conditions desirable for deposition coverage is to shorten the processing time for stacking the deposition layer D1 of the required film thickness on the bottoms VSb and VLb. In other words, it is to increase the film formation speed for stacking the deposition layer D1 on the bottoms VSb and VLb.

The deposition coverage is adjusted according to the etching depth and the aspect ratio. That is, even if the aspect ratio changes in response to the change in the depth of the bottoms VSb and VLb, it is possible to form a deposition layer D1 of a desired thickness at a predetermined lamination deposition rate.
Furthermore, the uniformity and reliability of the deposition layer D1 laminated on the bottom portion VSb and the uniformity and reliability of the deposition layer D1 laminated on the bottom portion VLb are improved, respectively.

8A to 8C are cross-sectional views showing steps of the dry etching method for silicon in this embodiment.
In the dry etching step S04 shown in FIG. 5, the bottoms VSb, VLb corresponding to the opening patterns MS, ML are dug down by anisotropic plasma etching to form bottoms VSb1, VLb1, as shown in FIG.

At this time, the depths of the bottom VSb1 corresponding to the opening pattern MS and the bottom VLb1 corresponding to the opening pattern ML formed in the dry etching process S04 are set to be uniform depending on the processing conditions in the dry etching process S04, the anisotropy of the plasma, and the film thickness difference of the deposition layer D1 laminated by the deposition process S03.

Specifically, the thickness TSD1 of the deposition layer D1 laminated on the bottom VSb corresponding to the opening pattern MS is smaller than the thickness TLD1 of the deposition layer D1 laminated on the bottom VLb corresponding to the opening pattern ML, and the amount of etching for the bottom VSb corresponding to the opening pattern MS is smaller than the amount of etching for the bottom VLb corresponding to the opening pattern ML. These are offset, and the depth of the bottom VSb1 corresponding to the opening pattern MS and the depth of the bottom VLb1 corresponding to the opening pattern ML become uniform.

In addition, in the dry etching step S04, the effect of etching on the side walls VSq, VLq corresponding to the opening patterns MS, ML is significantly reduced by the processing conditions, the anisotropy of the plasma, and the deposition layer D1. As a result, the side walls VSq, VLq are perpendicular to the surface of the silicon substrate S, are substantially flush with the surface, and are formed to extend in the depth direction without irregularities.
That is, the bottoms VSb1, VLb1 are formed so that the recess patterns VS, VL have uniform diameter dimensions.

In order to realize this shape, in the dry etching step S04, the plasma processing apparatus 10 shown in FIGS. 1 and 2 is used as described above in order to impart strong anisotropy to the plasma processing.
In the dry etching step S04, the frequency λ1 of the high frequency power applied to the first electrode E1 and the second electrode E2 is set to be larger than the frequency λ3 of the high frequency power applied to the third electrode E3 in the plasma processing apparatus 10. Specifically, the frequency λ2 can be set to 13.65 MHz, and the frequency λ3 can be set to 2 MHz.

In the dry etching step S04, the AC power having the frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This prevents the etching rate of the deposition layer D1 from varying in the radial direction. The power distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in the etching rate.

In addition, in the plasma processing device 10 in the dry etching process S04, the power supply of frequency λ1 can be set to a value greater than that in the deposition process S03 and equal to that in the ashing process S05.

In addition, in the plasma processing apparatus 10 in the dry etching process S04, the supply power of the AC power having the frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to a value greater than the frequency λ2 of the AC power applied to the third electrode E3.

In addition, in the plasma processing apparatus 10 in the dry etching step S04, it is preferable to apply a bias voltage having a frequency λ3 to the internal electrode 12. The frequency λ3 can be set to a value lower than the frequency λ2 of the AC power applied to the third electrode E3. The frequency λ3 can be set to, for example, 400 kHz.

In the anisotropic plasma etching in the dry etching step S04, a mixed gas of _SF6 and _O2 is plasma-decomposed to perform anisotropic etching of Si. As a result, F radicals generated by the decomposition of _SF6 etch Si (F+Si→ _SiF4 ). Since this etching reaction is isotropic etching, an insulating layer (protective film) may be attached to the side walls VSq and VLq to suppress the etching reaction of the side walls VSq and VLq in order to perform anisotropic etching.

In the anisotropic plasma etching using a mixed gas of SF ₆ /O ₂ in the dry etching step S04, the deposition layer D1 is removed from the sidewalls VSq, VLq corresponding to the opening patterns MS, ML to expose the sidewalls VSq, VLq.

Here, in the anisotropic plasma etching using a mixed gas of SF ₆ /O ₂ in the dry etching step S04, an insulating layer may be formed to protect the side walls VSq and VLq. At the same time, the side walls VSq and VLq are protected by oxidation of the side walls VSq and VLq by O and formation of a deposition film of SiO _x by reaction between O and Si that is re-decomposed from SiF ₄ , which is an etching product.

In addition, in the dry etching step S04, in order to prevent a shortage of SiF ₄ , which is an etching product, SiF ₄ can also be supplied as a gas.

Furthermore, in the dry etching step S04, _SF6 or _NF3 is used as the etching gas, and _SiF4 is added to the etching gas as a silicon compound, and _O2 , _N2 , _N2O , NO, _NOx or _CO2 is added as a reactant, so that the bottoms VSb and VLb can be intensively etched.
Furthermore, in the dry etching step S04, the anisotropy can be enhanced by lowering the substrate temperature during processing by using an electrostatic chuck having a coolant path therein as the internal electrode 12. For example, the coolant temperature is set to 10° C. or lower.

9A to 9C are cross-sectional views showing steps of the dry etching method for silicon in this embodiment.
In the ashing step S05 shown in FIG. 5, the remaining deposition layer D1 is removed after the completion of the dry etching step S04, as shown in FIG.
In particular, in the ashing step S05, the conditions are set so as to reliably remove the deposit layer D1 remaining near the inner periphery of the opening patterns MS and ML of the resist layer (mask layer) M.

In the ashing step S05, after the completion of the dry etching step S04, the deposition layer D1 adhering to the surface of the resist layer (mask layer) M, the deposition layer D1 remaining near the inner circumference of the opening patterns MS and ML of the resist layer (mask layer) M, and the deposition layer D1 remaining on the side walls VSq and VLq corresponding to the opening patterns MS and ML are removed. In addition, if there is any deposition layer D1 remaining on the bottom VSb1 corresponding to the opening pattern MS, and the deposition layer D1 remaining on the bottom VLb1 corresponding to the opening pattern ML, this is removed.

In the ashing step S05, it is not preferable if the deposit layer D1 remaining at the inner peripheral position of the opening pattern MS and the deposit layer D1 remaining at the inner peripheral position of the opening pattern ML are not completely removed and remain.
That is, in the deposition process S03 of the next or subsequent cycle, which is a subsequent process in multiple repeated cycles, further deposition layer D2 is deposited on the remaining deposition layer D1, thereby reducing the opening diameter (opening area) of the opening patterns MS and ML in the resist layer (mask layer) M.

As a result, even if etching with stronger anisotropy is performed in the dry etching step S04 of the second cycle, which is the step subsequent to the ashing step S05 of the first cycle of the repeated cycle, the deposition layers D1 and D2 prevent the etching plasma from reaching the bottoms VSb1 and VLb1. Therefore, etching at the bottoms VSb1 and VLb1 may not be performed properly. As a result, the side walls VSq and VLq corresponding to the opening patterns MS and ML are no longer vertical, and it is not possible to eliminate the possibility that the shapes of the recess patterns VS and VL will become tapered.

In contrast, if the deposition layer D1 does not remain at the inner peripheral position of the opening pattern MS and the deposition layer D1 does not remain at the inner peripheral position of the opening pattern ML, then in the next or subsequent cycles, which are subsequent steps in the repeated cycle, in the deposition step S03, which is the second cycle, the deposition layer D2 will not be further deposited on the remaining deposition layer D1, and the opening diameter (opening area) of the opening pattern MS and the opening pattern ML in the resist layer (mask layer) M can be maintained at a predetermined size.

Then, in the dry etching step S04 of the second cycle, which is the next cycle of the repeated cycles, etching with enhanced anisotropy is performed as a post-process, so that the deposition layers D1 and D2 do not prevent the etching plasma from reaching the bottoms VSb1 and VLb1. Therefore, etching at the bottoms VSb1 and VLb1 is performed favorably, and the side walls VSq and VLq corresponding to the opening patterns MS and ML are extended in a vertical state, preventing the shapes of the recess patterns VS and VL from tapering, making it possible to form recess patterns VS and VL of the same diameter with a high aspect ratio.

In the ashing step S05 of the first cycle, as described above, in order to reliably remove the deposit layer D1 remaining at the inner peripheral positions of the opening patterns MS and ML, it is necessary to perform a plasma treatment with a high degree of dissociation of the gas _O2 used. For this reason, the ashing step S05 of the first cycle also uses the plasma treatment apparatus 10 shown in FIGS. 1 and 2 as described above.

At this time, in the plasma processing apparatus 10 in the ashing step S05 of the first cycle, the frequency λ1 of the AC voltage applied to the first electrode E1 and the second electrode E2 can be set to be greater than the frequency λ2 of the AC voltage applied to the third electrode E3. Specifically, the frequency λ1 can be set to 13.65 MHz, and the frequency λ2 can be set to 2 MHz.

In the ashing step S05, the AC power having the frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This makes it possible to prevent the ashing rate for the deposition layer D1 from varying in the radial direction. Here, the distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in ashing.

In addition, in the plasma processing device 10 in the ashing step S05 of the first cycle, the supply power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to a value greater than that in the deposition step S03 and equal to or greater than that in the dry etching step S04.

In addition, in the plasma processing apparatus 10 during the ashing process S05 of the first cycle, the supply power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to the same value as the supply power of frequency λ2 applied to the third electrode E3.

In addition, in the plasma processing apparatus 10 in the ashing step S05 of the first cycle, it is preferable to apply a bias voltage with a frequency λ3 to the internal electrode 12. The frequency λ3 can be set to a value lower than the frequency λ2 of the high frequency applied to the third electrode E3. The power of the bias voltage in the ashing step S05 of the first cycle can be set to be equal to the power of the bias voltage in the dry etching step S04 of the first cycle or higher than the power of the bias voltage in the dry etching step S04 of the first cycle.

In the ashing step S05 of the first cycle, _O2 gas can be supplied to perform ashing. In the _O2 gas-based anisotropic plasma treatment, the deposit layer D1 is reliably removed near the inner circumference of the opening patterns MS, ML and on the side walls VSq, VLq corresponding to the opening patterns MS, ML, thereby exposing the side walls VSq, VLq. At the same time, since _O2 gas is supplied to perform ashing in the ashing step S05 of the first cycle, the resist layer (mask layer) M made of resin may be removed to some extent and reduced in thickness in this step.

5, the silicon dry etching method according to the present embodiment repeats one cycle of a deposition step S03, a dry etching step S04, and an ashing step S05, thereby increasing the depth of the recess patterns VS and VL.
Furthermore, when the etching steps from the deposition step S03 to the ashing step S05 in the first cycle are completed, as shown in FIG. 5, the method includes a depth determination step S06a and a resist protection determination step S06.

In the depth determination step S06a, it is determined whether to proceed to the next resist protection determination step S06. At this time, the determination criterion in the depth determination step S06a is the depth of the recess patterns VS, VL, in other words, the aspect ratio of the recess patterns VS, VL.
If the recess patterns VS and VL are not deep enough, the process proceeds to a resist protection determination step S06 to determine whether or not to proceed to a resist protective film formation step S07, which will be described later, in order to repeat the cycle to the next etching step. If the recess patterns VS and VL are deep enough, the etching is terminated and the process proceeds to a post-step S08.

In the resist protection determination step S06, it is determined whether to continue the cycle to the next etching cycle or to proceed to the resist protective film formation step S07 described later.
Here, the criterion for the resist protection determining step S06 is the depth of the recess patterns VS and VL.

If the recess patterns VS, VL are not deep enough, problems will occur when the resist protective film Mm is formed in the resist protective film forming step S07 described below. Specifically, in the resist protective film forming step S07 described below, the resist protective film Mm is formed not only on the surface of the resist layer (mask layer) M but also on the bottoms VSb, VLb of the opening patterns MS, ML. If the resist protective film Mm is formed on the bottoms VSb, VLb of the opening patterns MS, ML, this may have an undesirable effect on the etching, such as preventing etching at the bottoms VSb, VLb from progressing.

The criterion for the resist protection determination step S06 is the depth of the recess patterns VS, VL, in other words, the aspect ratio of the recess patterns VS, VL. Specifically, if the aspect ratio of the recess patterns VS, VL is, for example, about 1 to 2, the cycle proceeds to the next etching step, and if the aspect ratio of the recess patterns VS, VL is about 3 to 4, the cycle proceeds to the resist protection film formation step S07, which will be described later. In other words, the determination is made based on the opening area of the recess patterns VS, VL and the amount of etching of the bottoms VSb, VLb in the first cycle etching step.

The judgment in the resist protection judgment step S06 may be made based on the results of measuring the depth of the recess patterns VS, VL in the silicon substrate S after the first cycle, which is the previous process, or the transition to the second cycle may be judged by analogy with the etching conditions in the previous process. When making a judgment based on the etching conditions, the etching depth is set in advance under predetermined conditions.

Next, we will explain what happens when the cycle advances to the second cycle.

10A to 10C are cross-sectional views showing the steps of the dry etching method for silicon in this embodiment.
The deposition step S03 of the second cycle shown in Fig. 5 is performed after the determination in the depth determination step S06a and the resist protection determination step S06 of the first cycle. The deposition step S03 of the second cycle makes it possible to protect the side walls of the recess pattern VS and the recess pattern VL from etching in the subsequent dry etching step S04 in the second cycle. In the deposition step S03 of the second cycle, as shown in Fig. 10, a deposition layer D2 made of a polymer such as fluorocarbon is formed on the entire surface of the silicon substrate S by anisotropic plasma processing.

In the dry etching process S04, which is a post-process in the second cycle and is an etching process using a fluorine compound, the deposition layer D2 protects the side walls VSq, VLq of the recess patterns VS, VL from etching and limits the etching to the bottoms VSb1, VLb1 of the recess patterns VS, VL in order to achieve vertical side walls MSq, MLq.

The deposition layer D2 is deposited on the surface of the resist layer (mask layer) M and on the bottoms VSb1, VLb1 of the recess patterns VS, VL. In addition, although the deposition layer D2 is shown on the side walls VSq, VLq of the recess patterns VS, VL in FIG. 10, it is not deposited very much in practice.

In the deposition step S03 of the second cycle, anisotropic plasma processing is performed using a fluorocarbon gas, similar to the deposition step S03 of the first cycle. In the deposition step S03 of the second cycle, the plasma processing device 10 shown in Figures 1 and 2 is used, as described above, similar to the deposition step S03 of the first cycle.

In the deposition process S03 of the second cycle, the plasma processing apparatus 10 can set conditions such as the applied frequency λ1 and frequency λ2, and the atmospheric pressure in the same manner as in the deposition process S03 of the first cycle. Here, the processing conditions in the deposition processes S03 of the second and subsequent cycles may be the same as those in the deposition process S03 of the first cycle, or may be set differently.

Furthermore, in the deposition step S03 of the second cycle, similarly to the deposition step S03 of the first cycle, the AC power of frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This prevents the deposition rate for the deposition layer D2 from varying in the radial direction. The distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in the deposition rate. In addition, the deposition step S03 in the second cycle may have the same distribution ratio as the deposition step S03 in the first cycle, or may have a different distribution ratio.

The deposition process S03 of the second cycle can be set to the same settings as the deposition process S03 of the first cycle, but in order to accommodate the decrease in the deposition rate on the bottoms VSb1, VLb1 of the recess patterns VS, VL, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 or the AC power of frequency λ2 applied to the third electrode E3, or both, can be increased, or a bias voltage can be applied to the internal electrode 12 to attract deposition particles.

The deposition layer D2 formed in the deposition process S03 of the second cycle has a larger film thickness at the bottom VLb corresponding to the opening pattern ML with a larger diameter than at the bottom VSb corresponding to the opening pattern MS with a smaller diameter, as in the deposition process S03 of the first cycle. Note that the film thickness of the deposition layer D2 at the bottom VLb of the opening pattern ML is equal to or smaller than the film thickness of the deposition layer D2 on the surface of the resist layer (mask layer) M on the outside of the opening patterns MS, ML.

In other words, the thickness of the deposition layer D3 decreases in the following order: the thickness TD2 of the deposition layer D2 on the surface of the resist layer (mask layer) M outside the opening patterns MS, ML, the thickness TLD2 of the deposition layer D2 at the bottom VLb1 of the opening pattern ML, and the thickness TSD2 of the deposition layer D2 at the bottom VSb1 of the opening pattern MS.

In the deposition process S03 of the second cycle, the above condition settings are used to control the deposition coverage of the deposition layer D2 at the bottoms VSb1 and VLb1 corresponding to the opening patterns MS and ML, respectively, to be optimized. Here, the direction of the conditions desirable for deposition coverage is to shorten the processing time for stacking the deposition layer D2 of the required film thickness on the bottoms VSb1 and VLb1. In other words, it is to increase the film formation speed for stacking the deposition layer D2 on the bottoms VSb1 and VLb1.

In the deposition step S03 of the second cycle, a desirable condition for deposition coverage is to adjust the deposition coverage in response to the etching depth and aspect ratio. In other words, as described below, even if the aspect ratio changes in response to a change in the depth of the bottoms VSb1 and VLb1 from the bottoms VSb and VLb, a deposition layer D2 of the desired thickness can be formed at a predetermined lamination deposition rate.

Furthermore, the object is to improve the uniformity and reliability of the deposition layer D2 laminated on the bottom portion VSb1, and the uniformity and reliability of the deposition layer D2 laminated on the bottom portion VLb1.
Furthermore, the deposition step S03 in the second cycle may be set to a longer time than the deposition step S03 in the first cycle. The same applies to the deposition steps S03 in the third and subsequent cycles.

11A to 11C are cross-sectional views showing steps of the dry etching method for silicon in this embodiment.
In the dry etching step S04 of the second cycle shown in FIG. 5, the bottoms VSb1, VLb1 corresponding to the opening patterns MS, ML are dug down by anisotropic plasma etching to form bottoms VSb2, VLb2, as shown in FIG.

At this time, the depths of the bottom VSb2 corresponding to the opening pattern MS and the bottom VLb2 corresponding to the opening pattern ML formed in the second cycle dry etching step S04 are set to be uniform depending on the processing conditions in the second cycle dry etching step S04, the anisotropy of the plasma, and the film thickness difference of the deposition layer D2 laminated in the second cycle deposition step S03, etc.

Specifically, the thickness TSD2 of the deposition layer D2 laminated on the bottom VSb1 corresponding to the opening pattern MS is smaller than the thickness TLD2 of the deposition layer D2 laminated on the bottom VLb1 corresponding to the opening pattern ML, and the amount of etching for the bottom VSb1 corresponding to the opening pattern MS is smaller than the amount of etching for the bottom VLb1 corresponding to the opening pattern ML. These are offset, and the depth of the bottom VSb2 corresponding to the opening pattern MS and the depth of the bottom VLb2 corresponding to the opening pattern ML become uniform.

In addition, in the dry etching step S04 of the second cycle, the effect of etching on the side walls VSq, VLq corresponding to the opening patterns MS, ML is significantly reduced by the processing conditions, the anisotropy of the plasma, and the deposition layer D2. As a result, the side walls VSq, VLq are perpendicular to the surface of the silicon substrate S, are substantially flush with the surface, and are formed to extend in the depth direction without irregularities.
That is, the bottoms VSb2, VLb2 are formed so that the recess patterns VS, VL have uniform diameter dimensions.

In order to realize this shape, the plasma treatment is made to have strong anisotropy in the second cycle dry etching step S04 as well. The second cycle dry etching step S04 uses a plasma treatment apparatus 10, which will be described later.
At this time, in the plasma processing apparatus 10 in the dry etching step S04 of the second cycle, the conditions can be the same as those in the dry etching step S04 of the first cycle.

In the dry etching step S04 of the second cycle, similarly to the dry etching step S04 of the first cycle, the AC power of frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This prevents the etching rate from varying in the radial direction. The power distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in the etching rate. In the dry etching step S04 of the second cycle, the power distribution ratio can be the same as that of the dry etching step S04 of the first cycle, or can be different.

Furthermore, in the dry etching step S04 of the second cycle, in the plasma processing apparatus 10, as in the dry etching step S04 of the first cycle, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to a value greater than that in the deposition step S03 of the second cycle and the same as that in the ashing step S05 of the second cycle.

Furthermore, in the second cycle dry etching step S04, in the plasma processing apparatus 10, as in the first cycle dry etching step S04, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to the same value as the high frequency supply power of frequency λ2 applied to the third electrode E3.

In the second cycle dry etching step S04, similarly to the first cycle dry etching step S04, it is preferable that the plasma processing apparatus 10 applies a bias voltage with a frequency λ3 to the internal electrode 12. The frequency λ3 can be set to a value lower than the frequency λ2 applied to the third electrode E3. The frequency λ3 can be set to, for example, 400 kHz.

In the anisotropic plasma etching in the dry etching step S04 of the second cycle, a mixed gas of _SF6 and _O2 is plasma-decomposed to anisotropically etch Si, as in the first cycle. As a result, F radicals generated by the decomposition of _SF6 etch Si (F+Si→ _SiF4 ). This etching reaction is isotropic etching, so a protective film may be attached to the side walls VSq and VLq to suppress the etching reaction of the side walls VSq and VLq in order to perform anisotropic etching.

In the _SF6 / _O2 mixed gas anisotropic plasma etching in the second cycle dry etching step S04, similar to the first cycle dry etching step S04, the deposition layer D2 is removed from the side walls VSq, VLq corresponding to the opening patterns MS, ML, exposing the side walls VSq, VLq.

Here, in the SF ₆ /O ₂ mixed gas anisotropic plasma etching in the second cycle dry etching step S04, an insulating layer may be formed to protect the side walls VSq and VLq, as in the first cycle dry etching step S04. At the same time, the side walls VSq and VLq are protected by oxidation of the side walls VSq and VLq by O and formation of a SiO _x deposition film by reaction between O and Si re-decomposed from SiF ₄ , which is an etching product.

In addition, in the dry etching step S04 of the second cycle, similarly to the dry etching step S04 of the first cycle, in order to prevent a shortage of _SiF4 , which is an etching product, _SiF4 can also be supplied as a gas.

Furthermore, in the dry etching step S04 of the second cycle, similarly to the dry etching step S04 of the first cycle, _SF6 or _NF3 is used as the etching gas, _SiF4 is added to the etching gas as a silicon compound, and _O2 , _N2 , _N2O , NO, _NOx or _CO2 is added to the etching gas as a reactant, so that the bottom portions VSb1 and VLb1 can be intensively etched.
Furthermore, the dry etching step S04 in the second cycle may be performed for a longer period of time than the dry etching step S04 in the first cycle. The same applies to the dry etching steps S04 in the third and subsequent cycles.

12A to 12C are cross-sectional views showing the steps of the dry etching method for silicon in this embodiment.
The second cycle ashing step S05 shown in FIG. 5 removes the remaining deposit layer D2 after the second cycle dry etching step S04 is completed, as shown in FIG.
In particular, in the ashing step S05 of the second cycle, the conditions are set so as to reliably remove the deposition layer D2 remaining near the inner periphery of the opening pattern MS and the opening pattern ML of the resist layer (mask layer) M.

In the second cycle ashing step S05, similarly to the first cycle ashing step S05, after the second cycle dry etching step S04 is completed, the deposit layer D2 adhering to the surface of the resist layer (mask layer) M, the deposit layer D2 remaining near the inner periphery of the opening patterns MS and ML of the resist layer (mask layer) M, and the deposit layer D2 remaining on the side walls VSq, VLq corresponding to the opening patterns MS, ML are removed.
Furthermore, if there is any remaining deposition layer D2 on the bottom VSb2 corresponding to the opening pattern MS, and if there is any remaining deposition layer D2 on the bottom VLb2 corresponding to the opening pattern ML, these are removed.

The most important thing here is to remove the deposition layer D2 remaining at the inner periphery of the opening pattern MS and the deposition layer D2 remaining at the inner periphery of the opening pattern ML. If this deposition layer D2 cannot be completely removed and remains, in the next deposition step S05, which is a post-step in the next cycle of the repeated cycle, further deposition layer D3 will be deposited on the remaining deposition layer D2, and the opening diameter (opening area) of the opening pattern MS and the opening pattern ML in the resist layer (mask layer) M will be reduced.

As a result, even if etching with enhanced anisotropy is performed in the third cycle, dry etching step S04, which is the post-processing step following the second cycle, the deposition layers D2 and D3 prevent the etching plasma from reaching the bottoms VSb1 and VLb1. Therefore, etching at the bottoms VSb1 and VLb1 is not performed properly, and the side walls VSq and VLq corresponding to the opening patterns MS and ML are no longer vertical, and it is not possible to eliminate the possibility that the shapes of the recess patterns VS and VL will become tapered.

In contrast, if the deposition layer D2 does not remain at the inner peripheral position of the opening pattern MS and the deposition layer D2 does not remain at the inner peripheral position of the opening pattern ML, in the deposition process S03, which is the third cycle and is the subsequent process in the next cycle of the repeated cycle, the deposition layer D3 will not be further deposited on the remaining deposition layer D2, and the opening diameter (opening area) of the opening pattern MS and the opening pattern ML in the resist layer (mask layer) M can be maintained at a predetermined size.

Then, in the dry etching step S04 of the third cycle, which is the next cycle of the repeated cycles, etching with enhanced anisotropy is performed as a post-process, so that the deposition layers D2 and D3 do not prevent the etching plasma from reaching the bottoms VSb2 and VLb2. Therefore, etching at the bottoms VSb2 and VLb2 is performed favorably, and the side walls VSq and VLq corresponding to the opening patterns MS and ML are extended in a vertical state, preventing the shapes of the recess patterns VS and VL from tapering, making it possible to form recess patterns VS and VL of the same diameter with a high aspect ratio.

In the second cycle ashing step S05, as described above, in order to reliably remove the deposit layer D2 remaining at the inner peripheral position of the opening patterns MS and ML, it is necessary to impart strong anisotropy to the plasma treatment, as in the first cycle ashing step S05. For this reason, the plasma treatment apparatus 10 shown in Figures 1 and 2 is used in the second cycle ashing step S05 as described above.

At this time, in the plasma processing apparatus 10 in the second cycle ashing step S05, similar to the first cycle ashing step S05, the frequency λ1 of the AC power applied to the first electrode E1 and the second electrode E2 can be set to be higher than the frequency λ2 of the AC power applied to the third electrode E3. Specifically, the frequency λ1 can be set to 13.65 MHz, and the frequency λ2 can be set to 2 MHz.

In addition, in the plasma processing apparatus 10 in the ashing step S05 of the second cycle, as in the first cycle, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to a value greater than the value in the deposition step S03 in the first cycle or any subsequent cycle, and the same value as the value in the dry etching step S04 of the second cycle.

Furthermore, in the plasma processing apparatus 10 in the second cycle ashing step S05, similar to the first cycle ashing step S05, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to the same value as the AC power of frequency λ2 applied to the third electrode E3.

In addition, in the plasma processing apparatus 10 in the second cycle ashing step S05, it is preferable to apply a bias voltage with a frequency λ3 to the internal electrode 12, as in the first cycle ashing step S05. The frequency λ3 can be set to a value lower than the frequency λ2 applied to the third electrode E3 on the side. The frequency λ3 can be set to, for example, 400 kHz. The power of the bias voltage in the second cycle ashing step S05 can be set equal to the power of the bias voltage in the second cycle dry etching step S04, or higher than the power of the bias voltage in the second cycle dry etching step S04.

In the second cycle ashing step S05, similarly to the first cycle ashing step S05, the AC power having the frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This makes it possible to prevent the ashing rate for the deposition layer D2 from varying in the radial direction. Here, the distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in ashing. In addition, in the ashing step S05 of the second cycle, the distribution ratio can be the same as that in the ashing step S05 of the first cycle, or can be a different distribution ratio.

In the second cycle ashing step S05, _O2 gas can be supplied to perform ashing. In the _O2 gas-based anisotropic plasma treatment, the deposit layer D2 is reliably removed near the inner circumference of the opening patterns MS, ML and on the side walls VSq, VLq corresponding to the opening patterns MS, ML, thereby exposing the side walls VSq, VLq. At the same time, in the second cycle ashing step S05, _O2 gas is supplied to perform ashing, so that in this step, the resist layer (mask layer) M made of resin may be removed to some extent and reduced in thickness.

When the second cycle ashing step S05 is completed, the second cycle resist protection determination step S06, like the first cycle depth determination step S06a and resist protection determination step S06, determines whether to continue with the next etching cycle, proceed to the resist protective film formation step S07 described below, or proceed to the subsequent step S08.

In the depth determination step S06a of the second cycle, it is determined whether to proceed to the next resist protection determination step S06. At this time, the determination criterion in the depth determination step S06a is the depth of the recess patterns VS, VL, in other words, the aspect ratio of the recess patterns VS, VL.
If the recess patterns VS and VL are not deep enough, the process proceeds to a resist protection determination step S06 to determine whether or not to proceed to a resist protective film formation step S07, which will be described later, in order to repeat the cycle to the next etching step. If the recess patterns VS and VL are deep enough, the etching is terminated and the process proceeds to a post-step S08.

In the resist protection determination step S06 of the second cycle, similar to the resist protection determination step S06 of the first cycle, the determination criterion is the depth of the recess patterns VS, VL, in other words, the aspect ratio of the recess patterns VS, VL.

In the resist protection determination step S06 of the second cycle, similarly to the resist protection determination step S06 of the first cycle, a determination is made to form a resist protective film Mm in the resist protective film formation step S07 when the depth of the recess patterns VS, VL is sufficient and when the aspect ratio of the recess patterns VS, VL is greater than the above-mentioned range.
That is, the determination is made based on the opening areas of the recess patterns VS, VL and the etching amounts of the bottoms VSb1, VLb1 in the second cycle etching process.

The judgment in the resist protection judgment step S06 may be made based on the results of measuring the depth of the recess patterns VS, VL in the silicon substrate S after the second cycle, which is the previous process, or the transition to the third cycle may be judged by analogy with the etching conditions in the previous process. When making a judgment based on the etching conditions, the etching depth is set in advance under predetermined conditions.

An additional criterion in the second cycle resist protection determination step S06 is that if the amount of thickness reduction of the resist layer (mask layer) M due to the second cycle ashing step S05 is smaller than a predetermined value, a decision is made to repeat the cycle toward the next third cycle dry etching step S04. Another criterion in the second cycle resist protection determination step S06 is that if the amount of thickness reduction of the resist layer (mask layer) M due to the second cycle ashing step S05 is larger than a predetermined value, a decision is made to proceed to the second cycle resist protective film formation step S07.

This is because if the amount of thickness reduction of the resist layer (mask layer) M is greater than a predetermined value when proceeding to the third cycle etching process, the thickness of the resist layer (mask layer) M may be insufficient, and the accuracy of the shape produced by the etching process cannot be maintained.

Next, we will explain what happens when we proceed to the resist protective film formation process S07.

The resist protective film forming step S07 in the second cycle is performed before proceeding to the third cycle, as shown in FIG.
13A to 13C are cross-sectional views showing the steps of the dry etching method for silicon in this embodiment.
In the resist protective film forming step S07 shown in FIG. 5, a resist protective film Mm is formed on the surface of a resist layer (mask layer) M by anisotropic plasma processing, as shown in FIG.
The resist protective film Mm is a film capable of protecting the resist layer (mask layer) M from etching in the subsequent dry etching step S04 and ashing step S05 in the third cycle and thereafter.

In the resist protective film forming step S07, the deposition rate of the resist protective film Mm is set higher than that of the deposition layer D2. The deposition rate of the resist protective film Mm is set higher by about 1.5 times than that of the deposition layer D2.
In the plasma CVD in the resist protective film forming step S07, plasma CVD is performed using a gas capable of forming Si _x O _y α _z , such as a mixed gas of SiF ₄ and O ₂ , a mixed gas of SiCl ₄ and O ₂ , a mixed gas of SiH ₄ and O ₂ , or TEOS (Tetraethyl orthosilicate, Tetraethoxysilane). This makes it possible to form the resist protective film Mm having a film configuration of SiOF.

Here, when a mixed gas of _SiF4 and _O2 is used in the resist protective film forming step S07, the _SiF4 gas, which is the same gas as that supplied in the dry etching step S04, can be used. In this case, it is preferable because the configuration related to the gas supply can be made common.

The SiOF film has a structure similar to that of a _SiO2 film. Therefore, the SiOF film does not become thinner in the deposition step S03, the dry etching step S04, and the ashing step S05 from the third cycle onwards, which are subsequent steps.
In other words, the resist protective film Mm can prevent the resist layer (mask layer) M from being reduced in thickness in the subsequent deposition step S03, dry etching step S04, and ashing step S05 from the third cycle onwards.

The resist protective film Mm is formed on the surface of the resist layer (mask layer) M by anisotropic plasma processing, but is not formed on the side walls VSq, VLq of the recess patterns VS, VL. In addition, the resist protective film Mm is not formed on the bottoms VSb2, VLb2 of the recess patterns VS, VL. This is because the aspect ratios of the recess patterns VS, VL are set to a predetermined value or more in the depth determination process S06a and the resist protection determination process S06.

In the resist protective film forming step S07 which is performed for the first time before proceeding to the third cycle, the plasma processing apparatus 10 shown in FIGS. 1 and 2 is used as described above in order to impart strong anisotropy to the plasma processing.
At this time, in the plasma processing apparatus 10 in the resist protective film forming step S07 in the second cycle, the frequency λ1 of the AC power applied to the first electrode E1 and the second electrode E2 can be set to be greater than the frequency λ2 of the AC power applied to the third electrode E3. Specifically, the frequency λ1 can be set to 13.65 MHz, and the frequency λ2 can be set to 2 MHz.

In the resist protective film formation step S07 of the second cycle, in the plasma processing apparatus 10, similar to the dry etching step S04 and ashing step S05 in the first or second cycle, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to a value greater than the value in the deposition step S03 of the first or second cycle, and the same value as in either the dry etching step S04 or the ashing step S05 of the first or second cycle.

Also, in the resist protective film formation process S07 in the second cycle, in the plasma processing device 10, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to the same value as the AC power of frequency λ2 applied to the third electrode E3.

In addition, in the resist protective film forming step S07 in the second cycle, similar to the deposition step S03 in the first or second cycle, a bias voltage may not be applied. In the resist protective film forming step S07 in the second cycle, the atmospheric pressure may be set to the same value as in the dry etching step S04 and ashing step S05 in the second cycle.

Furthermore, in the resist protective film formation step S07 in the second cycle, similar to any one of the deposition step S03, the dry etching step S04, and the ashing step S05 in the first or second cycle, the AC power of frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This makes it possible to prevent the deposition rate of the resist protective film Mm from varying in the radial direction. Here, the distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of process gas and the variation in the deposition rate. In addition, in the resist protective film forming step S07 in the second cycle, the distribution ratio can be the same as or different from any of the deposition step S03, the dry etching step S04, and the ashing step S05 in the first or second cycle.

When a resist protective film Mm having a SiOF structure is laminated on the surface of the resist layer (mask layer) M and an ashing step S05 is performed in the subsequent etching process from the third cycle onwards, wear of the resist layer (mask layer) M can be suppressed.

However, the resist protective film Mm having a SiOF structure is _gradually consumed by anisotropic plasma etching using a CF-based gas in the subsequent deposition step S03 from the third cycle onwards, i.e., a perfluorohydrocarbon gas such as _CHF3 , _C2F6 , _C2F4 , or _C4F8 , or _SF6 or _NF3 as the etching gas in the dry etching step S04 from the _third cycle onwards, with _SiF4 added as the silicon compound to the etching gas and _O2 , _N2 , _N2O , NO, _NOx , or _CO2 added as a reactant, for example, a mixed gas of _SF6 and _O2 .

Therefore, the thickness of the resist protective film Mm is set so that a predetermined number of cycles can be performed to form the recess patterns VS and VL to the desired depth. At this time, it is important that there is no variation in the film thickness in the radial direction.
Furthermore, when a predetermined number of cycles has elapsed, as described below, in order to restore the film thickness of the worn resist protective film Mm, in the corresponding cycle, a further resist protective film forming step S07 is performed in which the resist protective film Mm is re-laminated on the surface of the resist layer (mask layer) M.

5, the silicon dry etching method according to this embodiment repeats one cycle of a deposition step S03, a dry etching step S04, and an ashing step S05. This further increases the depth of the recess patterns VS and VL. Furthermore, a resist protective film Mm is laminated on the surface of the resist layer (mask layer) M in a resist protective film forming step S07 every predetermined number of cycles, i.e., at a predetermined frequency.
Following the resist protective film forming step S07, the process proceeds to the etching step which is the third cycle.

Next, we will explain what happens when the cycle progresses to the third cycle.

14A to 14C are cross-sectional views showing the steps of the dry etching method for silicon in this embodiment.
In the deposition process S03 of the third cycle shown in FIG. 5, a deposition layer D3 made of a polymer such as fluorocarbon is formed on the surface of the resist protective film Mm by anisotropic plasma treatment as shown in FIG. 14 so that the side walls of the recess patterns VS and VL can be protected from etching in the subsequent dry etching process S04 of the third cycle.
At this time, the thickness of the resist protective film Mm is somewhat reduced, but most of the resist protective film Mm remains in the deposition step S03 as one cycle.

In the dry etching process S04, which is a post-process in the third cycle and is an etching process using a fluorine compound, the deposition layer D2 protects the side walls VSq, VLq of the recess patterns VS, VL from etching and limits the etching to the bottoms VSb2, VLb2 of the recess patterns VS, VL in order to achieve vertical side walls MSq, MLq.

The deposition layer D3 is laminated on the surface of the resist protective film Mm and on the bottoms VSb2, VLb2 of the recess patterns VS, VL. In addition, in FIG. 14, the deposition layer D3 is shown on the side walls VSq, VLq of the recess patterns VS, VL, but in reality it is not laminated very much.

In the deposition step S03 of the third cycle, similarly to _the second cycle, anisotropic plasma processing is performed using a fluorocarbon gas such as _CHF3 , _C2F6 , _C2F4 , or _C4F8 . In the deposition step S03, in order to _impart strong anisotropy to the plasma processing, as described above, the plasma processing apparatus 10 shown in Figures 1 and 2 is used.

In the deposition process S03 of the third cycle, the frequency λ1 of the AC power applied to the first electrode E1 and the second electrode E2 can be set to be higher than the frequency λ2 of the AC power applied to the third electrode E3 in the plasma processing apparatus 10. Specifically, the frequency λ1 can be set to 13.65 MHz, and the frequency λ2 can be set to 2 MHz.
At this time, the same settings as those of the deposition step S03 in the first cycle and/or the second cycle can be used.

In the deposition process S03 of the third cycle, the plasma processing apparatus 10 can set conditions such as the applied frequency λ1 and frequency λ2, and the atmospheric pressure in the same manner as in the deposition process S03 of either the first or second cycle. Here, the processing conditions in the deposition process S03 of the third or subsequent cycles may be the same as or different from the deposition process S03 of either the first or second cycle.

Furthermore, in the deposition step S03 of the third cycle, similar to either the deposition step S03 of the first or second cycle, the AC power of frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This prevents the deposition rate of the deposition layer D2 from varying in the radial direction. The distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in the deposition rate. In addition, the deposition step S03 in the third cycle may have the same distribution ratio as the deposition step S03 in the first cycle and/or the deposition step S03 in the second cycle, or may have a different distribution ratio.

In addition, in the deposition process S03 of the third cycle, the plasma processing apparatus 10 can set the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 to a value smaller than the value in the subsequent dry etching process S04 and ashing process S05 of the third cycle. In addition, in the deposition process S03 of the third cycle, the plasma processing apparatus 10 can apply no bias voltage to the internal electrode 12.

The deposition layer D3 formed in the third cycle deposition process S03, like the second cycle deposition process S03, has a larger film thickness at the bottom VLb2 corresponding to the opening pattern ML with a larger diameter than at the bottom VSb2 corresponding to the opening pattern MS with a smaller diameter. The film thickness of the deposition layer D3 at the bottom VLb2 of the opening pattern ML is equal to or smaller than the film thickness of the deposition layer D3 on the surface of the resist protective film Mm on the outside of the opening patterns MS and ML.

In other words, the thickness of the deposition layer D3 decreases in the following order: thickness TD3 of the deposition layer D3 on the surface of the resist protective film Mm on the outer side of the opening patterns MS and ML, thickness TLD3 of the deposition layer D3 at the bottom VLb2 of the opening pattern ML, and thickness TSD3 of the deposition layer D3 at the bottom VSb2 of the opening pattern MS.

In the deposition process S03 of the third cycle, by setting the conditions as described above, it is possible to control the deposition coverage of the deposition layer D3 at the bottoms VSb2 and VLb2 corresponding to the opening patterns MS and ML so as to optimize them. Here, the direction of the conditions desirable for the deposition coverage is to shorten the processing time for stacking the deposition layer D3 of the required film thickness on the bottoms VSb2 and VLb2. In other words, it is to increase the film formation speed for stacking the deposition layer D3 on the bottoms VSb2 and VLb2.

In addition, in the deposition step S03 of the third cycle, a desirable condition for deposition coverage is to adjust the deposition coverage in response to the etching depth and aspect ratio. In other words, as described below, even if the aspect ratio changes in response to the change in depth of the bottoms VSb2, VLb2 from the bottoms VSb1, VLb1, a deposition layer D3 of the desired thickness is formed at a predetermined layering deposition rate.

Furthermore, the uniformity and reliability of the deposition layer D3 laminated on the bottom portion VSb2 and the uniformity and reliability of the deposition layer D3 laminated on the bottom portion VLb1 are improved, respectively.
Furthermore, in the deposition step S03 of the third cycle, the same can be performed for the deposition step S03 of the first cycle and/or the deposition step S03 of the second cycle.

15A to 15C are cross-sectional views showing the steps of the silicon dry etching method according to this embodiment.
In the dry etching step S04 of the third cycle shown in FIG. 5, the bottoms VSb2, VLb2 corresponding to the opening patterns MS, ML are dug down by anisotropic plasma etching to form bottoms VSb3, VLb3, as shown in FIG.
At this time, the thickness of the resist protective film Mm is somewhat reduced, but most of the resist protective film Mm remains in the dry etching step S04 of the third cycle (one cycle).

At this time, the depths of the bottom VSb3 corresponding to the opening pattern MS and the bottom VLb3 corresponding to the opening pattern ML formed in the third cycle dry etching step S04 are set to be uniform depending on the process conditions, power distribution ratio, plasma anisotropy, and film thickness difference of the deposition layer D3 stacked by the third cycle deposition step S03, etc.

Specifically, the thickness TSD3 of the deposition layer D3 laminated on the bottom VSb2 corresponding to the opening pattern MS is smaller than the thickness TLD3 of the deposition layer D3 laminated on the bottom VLb2 corresponding to the opening pattern ML, and the amount of etching for the bottom VSb2 corresponding to the opening pattern MS is smaller than the amount of etching for the bottom VLb2 corresponding to the opening pattern ML. These are offset, and the depth of the bottom VSb3 corresponding to the opening pattern MS and the depth of the bottom VLb3 corresponding to the opening pattern ML become uniform.

In the third cycle dry etching step S04, the effect of etching on the side walls VSq, VLq corresponding to the opening patterns MS, ML may be significantly reduced by the process conditions, the anisotropy of the plasma, and the deposition layer D3. As a result, the side walls VSq, VLq are perpendicular to the surface of the silicon substrate S, are substantially flush with the surface, and are formed without irregularities by extending in the depth direction.
That is, the bottoms VSb3, VLb3 are formed so that the recess patterns VS, VL have uniform diameter dimensions.

In order to realize this shape, the plasma processing apparatus 10 shown in FIGS. 1 and 2 is used as described above in the third cycle of dry etching step S04 in order to impart strong anisotropy to the plasma processing.
At this time, in the plasma processing apparatus 10 in the third cycle dry etching step S04, the frequency λ1 of the AC power applied to the first electrode E1 and the second electrode E2 can be set to be greater than the frequency λ2 of the AC power applied to the third electrode E3, as in the second cycle dry etching step S04. Specifically, the frequency λ1 can be set to 13.65 MHz, and the frequency λ2 can be set to 2 MHz.

Furthermore, in the dry etching step S04 of the third cycle, in the plasma processing apparatus 10, as in the second cycle, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to a value greater than that in the deposition step S03 of the third cycle and the same as that in the ashing step S05 of the third cycle.

Also, in the third cycle dry etching step S04, in the plasma processing apparatus 10, as in the second cycle, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to the same value as the AC power of frequency λ2 applied to the third electrode E3.

Furthermore, in the third cycle dry etching step S04, similar to the second cycle dry etching step S04, the AC power of frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This prevents the etching rate from varying in the radial direction. The power distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in the etching rate. In the dry etching step S04 of the third cycle, the power distribution ratio can be the same as or different from that of the dry etching step S04 of the first or second cycle.

In the third cycle dry etching step S04, similarly to the second cycle dry etching step S04, it is preferable that the plasma processing apparatus 10 applies a bias voltage with a frequency λ3 to the internal electrode 12. The frequency λ3 can be set to a value lower than the frequency λ2 applied to the third electrode E3. The frequency λ3 can be set to, for example, 400 kHz.

In the anisotropic plasma etching in the dry etching step S04 of the third cycle, a mixed gas of _SF6 and _O2 is plasma-decomposed to perform anisotropic etching of Si, as in the dry etching step S04 of the second cycle. As a result, F radicals generated by the decomposition of _SF6 etch Si (F+Si→ _SiF4 ). Since this etching reaction is isotropic etching, a protective film may be attached to the side walls VSq and VLq to suppress the etching reaction of the side walls VSq and VLq in order to perform anisotropic etching.

In the _SF6 / _O2 mixed gas anisotropic plasma etching in the third cycle dry etching step S04, similar to the second cycle dry etching step S04, the deposition layer D2 is removed from the side walls VSq, VLq corresponding to the opening patterns MS, ML, exposing the side walls VSq, VLq.

Here, in the SF ₆ /O ₂ mixed gas anisotropic plasma etching in the third cycle dry etching step S04, an insulating layer may be formed to protect the side walls VSq and VLq, as in the second cycle dry etching step S04. At the same time, the side walls VSq and VLq are protected by oxidation of the side walls VSq and VLq by O and formation of a SiO _x deposition film by reaction between O and Si that is re-decomposed from SiF ₄ , which is an etching product.

In addition, in the dry etching step S04 of the third cycle, similarly to the dry etching step S04 of the second cycle, in order to prevent a shortage of _SiF4 , which is an etching product, _SiF4 can also be supplied as a gas.

Furthermore, in the dry etching step S04 of the third cycle, similarly to the dry etching step S04 of the second cycle, _SF6 or _NF3 is used as the etching gas, _SiF4 is added to the etching gas as a silicon compound, and _O2 , _N2 , _N2O , NO, _NOx or _CO2 is added to the etching gas as a reactant, so that the bottom portions VSb2 and VLb2 can be intensively etched.
Furthermore, the third cycle dry etching step S04 may be performed for a longer period of time than the first cycle dry etching step S04 and/or the second cycle dry etching step S04.

16A to 16C are cross-sectional views illustrating steps of the silicon dry etching method according to this embodiment.
The third cycle ashing step S05 shown in FIG. 5 removes the remaining deposit layer D3 after the third cycle dry etching step S04 is completed, as shown in FIG.
In particular, in the ashing step S05 of the third cycle, the conditions are set so as to reliably remove the deposition layer D3 near the surface of the resist protective film Mm remaining near the inner peripheries of the opening patterns MS and ML.

In the third cycle ashing step S05, similar to the first and/or second cycle, after the third cycle dry etching step S04 is completed, the deposition layer D3 adhering to the surface of the resist protective film Mm, the deposition layer D3 remaining near the inner periphery of the openings of the opening patterns MS and ML, and the deposition layer D3 remaining on the side walls VSq, VLq corresponding to the opening patterns MS, ML are removed.

Furthermore, in the ashing step S05 of the third cycle, the deposition layer D3 remaining on the bottom VSb3 corresponding to the opening pattern MS and the deposition layer D3 remaining on the bottom VLb3 corresponding to the opening pattern ML are removed, if any.
At this time, the film thickness of the resist protective film Mm does not change, and most of the resist protective film Mm remains in the ashing step S05 of the third cycle.

The most important thing here is to remove the deposition layer D3 remaining at the inner periphery of the opening pattern MS and the deposition layer D3 remaining at the inner periphery of the opening pattern ML. If this deposition layer D3 cannot be completely removed and remains, the next deposition layer D4 will be deposited on the remaining deposition layer D3 in the deposition process S03, which is the next cycle of the multiple repeated cycles, and the opening diameter (opening area) of the opening pattern MS and the opening pattern ML in the resist layer (mask layer) M and the resist protective film Mm will be reduced.

As a result, even if etching with stronger anisotropy is performed in the subsequent cycles from the third cycle onwards, for example the dry etching step S04 of the fourth cycle, the deposition layers D2 and D3 prevent the etching plasma from reaching the bottoms VSb2 and VLb2. As a result, etching at the bottoms VSb2 and VLb2 is not performed properly, and the side walls VSq and VLq corresponding to the opening patterns MS and ML are no longer vertical, and the shape of the recess patterns VS and VL cannot be eliminated as being tapered.

In contrast, if the deposition layer D3 does not remain at the inner peripheral position of the opening pattern MS and the deposition layer D3 does not remain at the inner peripheral position of the opening pattern ML in the ashing step S05 of the third cycle, the deposition step S03 in the next or subsequent cycle of the repeated cycle, which is a subsequent process, will not cause further deposition of the deposition layer D4 on the remaining deposition layer D3, and the opening diameter (opening area) of the opening pattern MS and the opening pattern ML in the resist layer (mask layer) M and the resist protective film Mm can be maintained at a predetermined size.

Then, in the dry etching step S04 in the next or subsequent cycle of the repeated cycle, etching with enhanced anisotropy is performed as a post-step, so that the deposition layers D3 and D4 do not prevent the etching plasma from reaching the bottoms VSb2 and VLb2. Therefore, etching at the bottoms VSb2 and VLb2 is performed favorably, and the side walls VSq and VLq corresponding to the opening patterns MS and ML are extended in a vertical state, preventing the shapes of the recess patterns VS and VL from tapering, making it possible to form recess patterns VS and VL of the same diameter with a high aspect ratio.

At the same time, it is important that the resist protective film Mm maintains a sufficient thickness so that the resist layer (mask layer) M is not lost in the ashing process S05.

In the third cycle ashing step S05, as described above, in order to reliably remove the deposit layer D3 remaining at the inner peripheral position of the opening patterns MS and ML, it is necessary to impart strong anisotropy to the plasma treatment, as in the first and/or second cycle ashing steps S05. For this reason, the plasma treatment apparatus 10 shown in Figures 1 and 2 is used in the third cycle ashing step S05 as described above.

At this time, in the plasma processing apparatus 10 in the third cycle ashing step S05, similar to the first and/or second cycle ashing steps S05, the frequency λ1 of the AC power applied to the first electrode E1 and the second electrode E2 can be set to be higher than the frequency λ2 of the AC power applied to the third electrode E3. Specifically, the frequency λ1 can be set to 13.65 MHz, and the frequency λ2 can be set to 2 MHz.

Furthermore, in the plasma processing apparatus 10 in the ashing step S05 of the third cycle, similarly to the ashing step S05 of the first and/or second cycle, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to a value greater than that in the deposition step S03 of the third cycle and the same as that in the dry etching step S04 of the third cycle.

Furthermore, in the plasma processing apparatus 10 in the third cycle ashing step S05, as in the first and/or second cycle ashing steps S05, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to the same value as the AC power of frequency λ2 applied to the third electrode E3.

Furthermore, in the plasma processing apparatus 10 in the third cycle ashing step S05, it is preferable to apply a bias voltage having a frequency λ3 to the internal electrode 12, as in the first and/or second cycle ashing steps S05. The frequency λ3 can be set to a value lower than the frequency λ2 applied to the third electrode E3. The frequency λ3 can be set to, for example, 400 kHz.

In addition, in the plasma processing apparatus 10 in the ashing step S05 of the third cycle, it is preferable to apply a bias voltage to the internal electrode 12, as in the ashing step S05 of the first and/or second cycle. The power of the bias voltage in the ashing step S05 of the third cycle can be set equal to the power of the bias voltage in the dry etching step S04 of the third cycle, or higher than the power of the bias voltage in the dry etching step S04 of the third cycle.

In the ashing step S05 of the third cycle, _O2 gas can be supplied to perform ashing. In the _O2 gas-based anisotropic plasma treatment, the deposit layer D3 is reliably removed near the inner circumference of the opening patterns MS, ML and on the side walls VSq, VLq corresponding to the opening patterns MS, ML, and the side walls VSq, VLq are exposed. At the same time, in the ashing step S05 of the third cycle, _O2 gas is supplied to perform ashing, but since the resist layer (mask layer) M is laminated with a resist protective film Mm, the resist layer (mask layer) M is not removed by the _O2 plasma.

Furthermore, in the third cycle ashing step S05, similarly to the first and/or second cycle ashing step S05, the AC power of frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This makes it possible to prevent the ashing rate for the deposition layer D3 from varying in the radial direction. Here, the distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in ashing. In addition, in the ashing step S05 of the third cycle, the distribution ratio can be the same as that in the ashing step S05 of the first cycle and/or the second cycle, or can be a different distribution ratio.

5, the silicon dry etching method according to the present embodiment repeats a deposition step S03, a dry etching step S04, and an ashing step S05 as one etching cycle, thereby further increasing the depth of the recess patterns VS and VL.
When the etching steps from the deposition step S03 to the ashing step S05 in the third cycle are completed, as shown in FIG. 5, the process includes a depth determination step S06a and a resist protection determination step S06.

In the depth determination step S06a of the third cycle, it is determined whether to proceed to the next resist protection determination step S06. At this time, the determination criterion in the depth determination step S06a is the depth of the recess patterns VS, VL, in other words, the aspect ratio of the recess patterns VS, VL.
If the recess patterns VS and VL are not deep enough, the process proceeds to a resist protection determination step S06 to determine whether or not to proceed to a resist protective film formation step S07, which will be described later, in order to repeat the cycle to the next etching step. If the recess patterns VS and VL are deep enough, the etching cycle is ended and the process proceeds to a post-step S08.

In the resist protection determination step S06 of the third cycle, it is determined whether to continue the cycle to the next etching cycle or to proceed to the resist protective film formation step S07 described later.
Here, the criteria for the resist protection determination step S06 in the third cycle are the depth of the recess patterns VS, VL as well as the degree of etching of the resist protective film Mm, that is, the degree of reduction in thickness of the resist protective film Mm.

The depth or aspect ratio of the recess patterns VS, VL is sufficiently large at the end of the ashing step S05 from the third cycle onwards. Therefore, the criterion for the resist protection determination step S06 from the third cycle onwards is determined by the degree of etching of the resist protective film Mm, that is, the degree of reduction in thickness of the resist protective film Mm.

In the resist protection judgment step S06 of the third cycle, when the etching steps from the deposition step S03 to the ashing step S05 of the third cycle are completed, if the resist protective film Mm maintains a sufficient film thickness and has sufficient protective ability for the resist layer (mask layer) M, i.e., etching resistance, in the deposition step S03 and dry etching step S04 of the next and subsequent cycles, it is judged to proceed to the etching step of the next cycle, which is the fourth cycle.

In addition, in the resist protection judgment step S06 of the third cycle, if it is predicted that the resist protective film Mm does not maintain a sufficient film thickness and does not have sufficient protective ability for the resist layer (mask layer) M, i.e., etching resistance, a decision is made to proceed to the resist protective film formation step S07.

The judgment in the resist protection judgment step S06 of the third cycle may be made based on the result of measuring the film thickness of the remaining resist protective film Mm after the third cycle, which is the previous step, or the transition to the fourth cycle may be judged by inferring from the etching conditions in the previous step that the resist protective film Mm maintains a sufficient film thickness. In the judgment based on the etching conditions, the degree of thickness reduction of the resist protective film Mm under predetermined conditions is set in advance and judgment is made.

In addition, in the case of etching a silicon substrate S, if the deposition step S03, the dry etching step S04, and the ashing step S05 as described above are considered as one cycle, one resist protective film formation step S07 can be inserted after about 5 to 20 cycles, preferably about 8 to 12 cycles.

Next, we will explain the fourth cycle.

17A to 17C are cross-sectional views showing the steps of the dry etching method for silicon in this embodiment.
In the deposition process S03 of the fourth cycle shown in FIG. 5, a deposition layer D4 made of a polymer such as fluorocarbon is formed on the surface of the resist protective film Mm by anisotropic plasma processing, as shown in FIG. 17, so that the side walls of the recess patterns VS and VL can be protected from etching in the subsequent dry etching process S04 of the fourth cycle.
At this time, the thickness of the resist protective film Mm is somewhat reduced, but most of the resist protective film Mm remains in the deposition step S03 as one cycle.

In the dry etching process S04, which is a post-process in the fourth cycle and is an etching process using a fluorine compound, the deposition layer D4 protects the side walls VSq, VLq of the recess patterns VS, VL from etching and limits the etching to the bottoms VSb3, VLb3 of the recess patterns VS, VL in order to achieve vertical side walls MSq, MLq.

The deposition layer D4 is laminated on the surface of the resist protective film Mm and on the bottoms VSb3, VLb3 of the recess patterns VS, VL. In addition, in FIG. 17, the deposition layer D4 is shown on the side walls VSq, VLq of the recess patterns VS, VL, but in reality it is not laminated very much.

In the deposition step S03 of the fourth cycle, similarly to the third cycle, anisotropic plasma processing is performed using a fluorocarbon gas such as _CHF3 , _C2F6 , _C2F4 , or _C4F8 . In the deposition step _S05 , in order to _impart strong anisotropy to the plasma processing, as described above, the plasma processing apparatus 10 shown in Figures 1 and 2 is used.

In the deposition process S03 of the fourth cycle, the frequency λ1 of the AC power applied to the first electrode E1 and the second electrode E2 can be set to be higher than the frequency λ2 of the AC power applied to the third electrode E3 in the plasma processing apparatus 10. Specifically, the frequency λ1 can be set to 13.65 MHz, and the frequency λ2 can be set to 2 MHz.
At this time, the setting may be the same as any of the deposition steps S03 in the first to third cycles.

In the deposition step S03 of the fourth cycle, the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2 can be set to a value smaller than that in the dry etching step S04 and the ashing step S05 described later. In the plasma processing device 10, a bias voltage can be not applied to the internal electrode 12.
In the deposition step S03 of the fourth cycle, processing is performed under a predetermined atmospheric pressure. Furthermore, in the deposition step S03 of the fourth cycle, the atmospheric pressure may be set to be the same as any of the deposition steps S03 of the first to third cycles.

Furthermore, in the deposition step S03 of the fourth cycle, similar to any of the deposition steps S03 of the first to third cycles, the AC power of frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This makes it possible to prevent the deposition rate for the deposition layer D2 from varying in the radial direction. Here, the distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in the deposition rate. In addition, in the deposition step S03 of the fourth cycle, the distribution ratio can be the same as any one of the deposition steps S03 of the first to third cycles, or a different distribution ratio can be set.

The deposition layer D4 formed in the deposition step S03 of the fourth cycle, like any of the deposition steps S03 in the first to third cycles, has a larger film thickness at the bottom VLb3 corresponding to the opening pattern ML with a larger diameter than at the bottom VSb3 corresponding to the opening pattern MS with a smaller diameter. The film thickness of the deposition layer D4 at the bottom VLb3 of the opening pattern ML is equal to or smaller than the film thickness of the deposition layer D4 on the surface of the resist protective film Mm on the outside of the opening patterns MS and ML.

In other words, the thickness of the deposition layer D4 decreases in the following order: the thickness TD4 of the deposition layer D4 on the surface of the resist protective film Mm on the outer side of the opening patterns MS and ML, the thickness TLD4 of the deposition layer D4 at the bottom VLb3 of the opening pattern ML, and the thickness TSD4 of the deposition layer D4 at the bottom VSb3 of the opening pattern MS.

In the deposition process S03 of the fourth cycle, by setting the conditions as described above, it is possible to control the deposition coverage of the deposition layer D4 at the bottoms VSb3 and VLb3 corresponding to the opening patterns MS and ML so as to optimize them. Here, the direction of the conditions desirable for the deposition coverage is to shorten the processing time for stacking the deposition layer D4 of the required film thickness on the bottoms VSb3 and VLb3. In other words, it is to increase the film formation speed for stacking the deposition layer D4 on the bottoms VSb3 and VLb3.

In addition, in the deposition step S03 of the fourth cycle, a desirable condition for deposition coverage is to adjust the deposition coverage in response to the etching depth and aspect ratio. In other words, as described below, even if the aspect ratio changes in response to a change in the depth of the bottoms VSb3, VLb3 from the bottoms VSb2, VLb2, it is possible to form a deposition layer D3 of a desired thickness at a predetermined lamination deposition rate.

Furthermore, the uniformity and reliability of the deposition layer D4 stacked on the bottom portion VSb3 and the uniformity and reliability of the deposition layer D4 stacked on the bottom portion VLb3 are improved, respectively.

Next, in the fourth cycle of dry etching step S04 shown in FIG. 5, the bottoms VSb2, VLb2 corresponding to the opening patterns MS, ML are dug down by anisotropic plasma etching to form bottoms VSb3, VLb3.
At this time, the thickness of the resist protective film Mm is somewhat reduced, but as one cycle, the resist protective film Mm almost remains in the dry etching step S04 of the fourth cycle.

Furthermore, in the dry etching step S04 of the fourth cycle, similar to any of the dry etching steps S04 in the first to third cycles, the AC power of frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This makes it possible to prevent the etching rate from varying in the radial direction. Here, the distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in the etching rate. In addition, in the dry etching step S04 of the fourth cycle, the distribution ratio can be the same as any one of the distribution ratios in the first to third cycles, or a different distribution ratio can be set.

Next, in the ashing step S05 of the fourth cycle shown in FIG. 5, the remaining deposit layer D4 is removed.
At this time, the thickness of the resist protective film Mm is somewhat reduced, but the thickness of the resist protective film Mm is not reduced in the ashing step S05.

Also, in the ashing step S05 of the fourth cycle, similarly to any of the ashing steps S05 in the first to third cycles, the AC power of frequency λ1 applied by the power distributor 16 is distributed between the first electrode E1 and the second electrode E2.
This makes it possible to prevent the ashing rate for the deposition layer D3 from varying in the radial direction. Here, the distribution ratio between the first electrode E1 and the second electrode E2 by the power distributor 16 is set according to the type of processing gas and the variation in ashing. In addition, in the ashing step S05 of the fourth cycle, the distribution ratio can be the same as that of any one of the ashing steps S05 in the first to third cycles, or a different distribution ratio can be used.

Furthermore, as the depth determination step S06a and resist protection judgment step S06 of the fourth cycle, whether or not to insert the resist protective film formation step S07 is determined at a predetermined frequency depending on the thickness of the resist protective film Mm, and the etching process cycle is further repeated.

This forms a recess pattern VS having a diameter dimension ΦS and a recess pattern VL having a diameter dimension ΦL, both of the same depth, on the surface of the silicon substrate S.

Furthermore, as a post-process S08 shown in FIG. 5, if necessary, the resist protective film Mm is removed by a process similar to the dry etching process S04, and further, the resist layer (mask layer) M is removed by a wet etching process or a process similar to the ashing process S05, thereby completing the silicon dry etching method according to this embodiment.
In the silicon dry etching method according to this embodiment, the number of cycles can be about 50.

<Experimental Example 1>
As described above, in the plasma processing apparatus 10 shown in Figures 1 and 2, the change in the radial distribution of the processing characteristics was investigated when the distribution ratio of the AC power distributed between the first electrode E1 and the second electrode E2 by the power distributor 16 was changed. In addition, the change in the radial distribution of the processing characteristics by the dual-frequency ICP was investigated. The plasma processing was evaluated by appropriately selecting from the following steps.

Deposition process: silicon-containing thin film deposition S03
Etching process: Etching the bottom insulating layer of the TSV using a carbon-containing film as a mask S04
Ashing process: Carbon-containing film ashing S05
Deposition process: Carbon-containing thin film deposition S07

Here, a film formation evaluation was performed on a Φ300 mm silicon substrate as a split plasma processing evaluation using SiF ₄ /O _2. Here, the power distribution ratio between the first electrode E1, which is "IN", and the second electrode E2, which is "OUT", was changed in the range of IN:OUT = 999:0 to 0:999 (corresponding to a distribution ratio of 0.9:0.1 to 0.1 to 0.9).

The following are the parameters for film formation using the split method.
1 and 2, gas is supplied from the gas introduction means into the chamber 11 through a central gas inlet 15. The diameter D [mm] of the internal electrode 12, which is a substrate support means (substrate stage), is fixed at 400 mm, and the diameter d [mm] of the second electrode (antenna 2) is fixed at 400 mm.

Conditions in the deposition process Supply gas: _SiF4 / _O2
Supply gas flow rate: SiF ₄ /O ₂ =160/150 sccm
First frequency λ1: 13.56 MHz
Supply power of first frequency λ1: 1800 W
Supply power distribution ratio of first frequency λ1; IN:OUT=999:0 to 0:999 (corresponding to a distribution ratio of 0.9:0.1 to 0.1 to 0.9)
Supply power of second frequency λ2: 0 W
Film formation processing time: 120 sec
Inner electrode temperature: -10℃

The results of film formation using splitting are shown below.
18 to 22 are graphs showing the change in the radial film thickness distribution due to splitting in the examples. In the figures, X and Y indicate the directions in which the film thickness was examined in the radial direction of the substrate that is perpendicular to each other. The distribution ratios are IN:OUT=999:0 (distribution ratio 0.9:0.1) in FIG. 18, IN:OUT=750:253 (distribution ratio 0.75:0.25) in FIG. 19, IN:OUT=500:503 (distribution ratio 0.5:0.5) in FIG. 20, IN:OUT=250:753 (distribution ratio 0.25:0.75) in FIG. 21, and IN:OUT=0:999 (distribution ratio 0.1:0.9) in FIG. 22.

These results show that it is possible to vary the in-plane distribution of film thickness. Therefore, it is possible to control the film thickness distribution so that it can be corrected without splitting.

<Experimental Example 2>
Next, the influence of RF distribution (distribution ratio) and gas introduction was examined.
1 and 2, the gas supply from the gas introduction means into the chamber 11 was switched between the gas introduction port 14 and the gas introduction port 15. In addition, the type of gas supplied was changed to examine the effect of the RF splitter on the radial film thickness distribution (change in film formation rate).

The film formation parameters are shown below.
In the plasma processing apparatus 10 shown in Figures 1 and 2, the diameter D [mm] of the internal electrode 12, which is the substrate support means (substrate stage), is fixed at 400, and the diameter d [mm] of the second electrode (antenna 2) is fixed at 400.

Conditions for the deposition process: Supply gas flow rate: _C4F8 ; ₂₀₀ sccm
Supply gas flow rate: SiF ₄ /O ₂ =160/150 sccm
First frequency λ1: 13.56 MHz
Supply power of first frequency λ1: 2000 W
Supply power of second frequency λ2: 0 W
Film formation processing time: 120 sec
Inner electrode temperature: -10℃

The results of film formation using splitting are shown below.
Fig. 23 is a graph showing the radial film thickness distribution change in C ₄ F ₈ gas in the example. Fig. 24 is a graph showing the radial film thickness distribution change in SiF ₄ /O ₂ gas in the example.
23 and 24, the central Gas is gas supplied from the gas inlet 15, and the peripheral Gas is gas supplied from the gas inlet 14.
Depo1 shows the result of film formation using SiF ₄ /O ₂ gas, and Depo2 shows the result of film formation using C ₄ F ₈ gas.

From these results, it can be seen that the distribution of the film thickness of Depo2 using _C4F8 gas varies greatly depending on the position of the gas inlet for introducing the gas, _but the distribution of the film thickness of Depo1 using _SiF4 / _O2 gas does not vary significantly even if the position of the gas inlet is changed.
It is also found that the RF of 13.56 MHz affects the distribution of the film thickness of Depo 1 using SiF ₄ /O ₂ gas. In other words, it is found that the film thickness of Depo 1 using SiF ₄ /O ₂ gas cannot be matched with the in-plane distribution in other steps unless the plasma distribution is adjusted by a power distributor.

<Experimental Example 3>
Next, the influence of RF distribution (distribution ratio) and etching depth was examined.
1 and 2, gas is supplied from the gas introduction means into the chamber 11 through the central gas inlet 15. In addition, the power distribution ratio was changed to examine the effect of the RF splitter on the radial etching depth distribution (change in etching rate).

The etching parameters are shown below.
In the plasma processing apparatus 10 shown in Figures 1 and 2, the diameter D [mm] of the internal electrode 12, which is the substrate support means (substrate stage), is fixed at 400, and the diameter d [mm] of the second electrode (antenna 2) is fixed at 400.

Conditions for the etching process: Supply gas flow rate: SiF ₆ /SiF ₄ /O ₂ =275/50/40 sccm
First frequency λ1: 13.56 MHz
Supply power of first frequency λ1: 1800 W
Supply power distribution ratio of the first frequency λ1; IN:OUT=999:0, 750:250, 500:500, 250:550, 0:999
Supply power of second frequency λ2: 0 W
Film formation processing time: 135 sec
Inner electrode temperature: -10℃
Gas inlet position: center (gas inlet 15)

The results of split etching are shown below.
FIG. 25 is a graph showing the change in the radial etching depth distribution in the example.

These results show that the power distributor changes the radial distribution of the TSV etching depth, but the amount of change is smaller than the change in film thickness during the deposition process.

<Experimental Example 4>
Next, the effect of frequency superposition and etching depth was examined.
1 and 2, gas was supplied from the gas introduction means into the chamber 11 through the central gas inlet 15. In addition, AC power having a second frequency λ2 was supplied to examine the effect of superposition on the radial etching depth distribution (change in etching rate).

The etching parameters are shown below.
In the plasma processing apparatus 10 shown in Figures 1 and 2, the diameter D [mm] of the internal electrode 12, which is the substrate support means (substrate stage), is fixed at 400, and the diameter d [mm] of the second electrode (antenna 2) is fixed at 400.

Conditions for the etching process: Supply gas flow rate: SiF ₆ /SiF ₄ /O ₂ =275/50/40 sccm
First frequency λ1: 13.56 MHz
Supply power of first frequency λ1: 1800 W
Supply power distribution ratio of first frequency λ1; IN:OUT=999:0
Second frequency λ2: 2 MHz
Supply power of second frequency λ2: 200 W
Film formation processing time: 135 sec
Inner electrode temperature: -10℃
Gas inlet position: center (gas inlet 15)
Etching diameter: Φ5 μm

The results of etching using frequency superposition are shown below.
26 is a graph showing the change in the radial etching depth distribution in the embodiment. At the same time, SEM images of the substrate thickness direction at each measurement point are arranged. In the figure, the left and right positions of the SEM images are arranged corresponding to the measurement points of the graph. Also, the SEM images show only the results in the X direction.

These results show that the etching depth in the radial plane changes when two frequencies are superimposed, compared to the results with the power divider.

<Experimental Example 5>
Next, the influence of the presence or absence of frequency overlap on the etching depth was examined.
1 and 2, gas is supplied from the gas introduction means into the chamber 11 through the central gas inlet 15. In addition, the supply of AC power having the second frequency λ2 was switched to examine the effect of the presence or absence of overlap on the radial etching depth distribution (change in etching rate).

The etching parameters are shown below.
In the plasma processing apparatus 10 shown in Figures 1 and 2, the diameter D [mm] of the internal electrode 12, which is the substrate support means (substrate stage), is fixed at 400, and the diameter d [mm] of the second electrode (antenna 2) is fixed at 400.

Conditions for the etching process: Supply gas flow rate: SiF ₆ /SiF ₄ /O ₂ =275/50/40 sccm
First frequency λ1: 13.56 MHz
Supply power of first frequency λ1: 1800 W
Supply power distribution ratio RFS of first frequency λ1; IN:OUT=999:0
Second frequency λ2: 2 MHz
Supply power of second frequency λ2: 200 W, 0 W
Film formation processing time: 135 sec
Inner electrode temperature: -10℃
Gas inlet position: center (gas inlet 15)
Etching diameter: Φ5 μm
Bias power: 100-200W
Bias power frequency λ3: 400 kHz

The results of the change in etching depth depending on whether or not frequency superposition is performed are shown below.
FIG. 27 is a graph showing the change in the radial etching depth distribution depending on whether or not frequency superposition is performed in the example.

Compared with the results of the power distributor, these results show that the presence or absence of dual frequency superposition changes the etching depth from a state in which the etching rate is large at the radial center to a state in which the etching rate is small at the radial center and large at the radial periphery.

<Experimental Example 6>
Next, the influence of the presence or absence of frequency superposition and the change in film thickness was examined.
1 and 2, gas was supplied from the gas introduction means into the chamber 11 through the central gas inlet 15. In addition, the supply of AC power having the second frequency λ2 was switched to examine the effect of the presence or absence of overlap on the film thickness distribution in the radial direction (change in deposition rate).

Conditions in the deposition process Supply gas: _SiF4 / _O2
Supply gas flow rate: SiF ₄ /O ₂ =160/150 sccm
First frequency λ1: 13.56 MHz
Supply power of first frequency λ1: 1800 W
Supply power distribution ratio RFS of first frequency λ1; IN:OUT=999:0 (corresponding to a distribution ratio of 0.9:0.1)
Second frequency λ2: 2 MHz
Supply power of second frequency λ2: 200 W, 0 W
Film formation processing time: 120 sec
Inner electrode temperature: -10℃

The results of the change in deposition thickness with and without frequency superposition are shown below.
FIG. 28 is a graph showing the change in radial deposition film thickness distribution depending on the presence or absence of frequency superposition in the example.

The results in Figure 28, compared to the results for the power splitter, show that the deposition rate at the radial center remains large regardless of whether or not two frequencies are superimposed, but the deposition rate at the radial periphery becomes larger than the deposition rate at the radial center (the shoulders of the graph rise).

That is, from the results of Experimental Example 5 shown in FIG. 27 and the results of Experimental Example 6 shown in FIG. 28, the following can be seen by comparing the results of the power divider and the results of dual-frequency superposition.
Etching depth: Center fast ⇒ Edge fast 2 MHz has a large effect Deposition film thickness: Center fast ⇒ Center fast 2 MHz has a small effect In order to improve the processing uniformity within the substrate surface by matching the in-plane distribution of the etching process and the deposition process, it is necessary to adjust the deposition distribution and etching distribution using a power distributor.

<Experimental Example 7>
Next, the effects of the power divider and frequency superposition on the magnetic field formation state were examined.
Here, in the plasma processing apparatus 10 shown in Figures 1 and 2, the spatial distribution of the magnetic field formed was simulated between a plasma processing apparatus equipped with a splitter and a dual-frequency ICP capable of distributing the AC power of frequency λ1 applied to the first electrode E1 and the second electrode E2, and a plasma processing apparatus not equipped with a splitter.
The results are shown in Figures 29 to 32.
FIG. 29 shows, by simulation, the spatial distribution of a magnetic field formed only by the first electrode E1 using AC power of frequency λ1, among magnetic fields formed in a plasma processing apparatus not equipped with a splitter.
FIG. 30 shows, by simulation, the spatial distribution of a magnetic field formed only by the third electrode E3 by AC power of frequency λ2, among the magnetic fields formed in a plasma processing apparatus not provided with a splitter.
FIG. 31 shows a simulation of the spatial distribution of the magnetic field formed only by the first electrode E1 by AC power of frequency λ1, among the magnetic fields formed in the plasma processing apparatus having the splitter shown in FIGS.
FIG. 32 shows a simulation of the spatial distribution of the magnetic field formed only by the third electrode E3 by AC power of frequency λ2, among the magnetic fields formed in the plasma processing apparatus having the splitter shown in FIGS.
29 to 32, the areas surrounded by dotted lines indicate the range of space that directly contributes to the plasma processing of the substrate in the plasma processing apparatus.

Specifically, a conventional antenna is constructed with two four-turn antennas, one of which is a 13.56MHz antenna with the IN and OUT terminals of a 13.56MHz M/B connected to both ends, and a 2MHz antenna with the IN and OUT terminals of a 2MHz M/B connected to both ends, with the 13.56MHz antenna concentrically positioned on the inside and the 2MHz antenna on the outside; a dual-frequency ICP is constructed with three four-turn antennas, the first of which is connected to the inside circuit of the power splitter and the second is connected to the outside circuit of the power splitter, with a 13.56MHz power splitter inside and outside antenna, and a 2MHz antenna with a 2MHz M/B connected to both ends of the third antenna, with the third antenna concentrically positioned on the inside as the 13.56MHz power splitter inside antenna, the 2MHz antenna, and the 13.56MHz power splitter outside antenna. Using a power splitter antenna, and with a power ratio of 0.5:0.5 in the power splitter, we simulated the magnetic field strength generated by the antenna and vacuum chamber at each frequency when 1 kW of 13.56 MHz and 1 kW of 2 MHz were input, and the magnetic field strength inside the vacuum chamber where the antenna was separated by a dielectric window.

From the results of FIGS. 29 to 32, it is evident that the process uniformity can be improved by matching the distribution of the magnetic field strength in the space enclosed by the dotted lines at 13.56 MHz and 2 MHz.
In other words, it was confirmed that the magnetic fields of 13.56 MHz and 2 MHz do not coincide with each other in the conventional antenna, but the magnetic fields coincide with each other in the antenna for the dual-frequency ICP power splitter.

The conditions in the ashing step S07 are as follows.
Supply gas: _O2
Gas flow rate: _O2 : 450 sccm,
Treatment atmosphere pressure: 9 Pa
Supply power of first frequency λ1: 2000 W
First frequency λ1: 13.56 MHz
Supply power of second frequency λ2: 2000 W
Second frequency λ2: 2 MHz
Bias power: 200 W
Bias power frequency λ3: 400 kHz
In the ashing step S07 as well, in-plane uniformity was achieved.

According to the present invention, when multiple plasma processing steps are performed continuously or intermittently in the same chamber while maintaining the vacuum and keeping the chamber sealed, it is possible to match the in-plane distribution of the processing characteristics in each step and to make the processing characteristics approximately uniform over the entire surface of the substrate.

In other words, if a cycle of multiple processes such as a deposition process, an etching process, an ashing process, and a protective film formation (deposition) process is repeated many times, for example 30 cycles, and if there is variation in the in-plane distribution in each deposition process, etching process, and ashing process, the processes cannot be performed uniformly, and as a result, the desired shape cannot be obtained. For example, in the case of the cycle etching process described above as an example, it becomes impossible to maintain uniformity in the shape, particularly the depth or diameter dimension, of the recess pattern formed in the silicon substrate.

In contrast, if the plasma processing apparatus of the present invention is capable of using a power distributor and frequency superposition, then in the case of cycle etching processing, it is possible to achieve uniformity in the processing characteristics of each process on the surface, and it is possible to maintain uniformity in the shape, particularly the depth or diameter dimension, of the recess pattern formed on the silicon substrate.

Dual frequency ICP allows the electron density in the plasma volume generated at 13.56 MHz to be increased by 2 MHz, expanding the range of controllability of dissociation of molecules in the plasma.

In addition, according to the dual frequency ICP,
・13.56MHz: Plasma generation (low electron density)
2MHz: Heats the plasma generated at 13.56MHz deep into the volume (because the low frequency magnetic field penetrates deep inside)
・ By superimposing 2M on 13M, the electron density is controlled, and the effect of widening the gas dissociation control margin was confirmed.

The power divider can distribute the power generated from one power source to two antennas at an arbitrary distribution ratio, thereby adjusting the spatial density distribution of the generated plasma.
From these results, it can be seen that the etching rate and film formation rate relative to the plasma density distribution differ depending on the type of gas used, but in other processing steps in which different gases are supplied, it is possible to accommodate changes in the in-plane distribution due to the characteristics of the gas used.

According to the present invention, it is possible to provide a mechanism for adjusting the distribution using a high-frequency power distributor while maintaining the characteristics obtained by dual-frequency ICP. In particular, even if different gases are used for each process, the power distribution ratio is adjusted by the power distributor for two antennas arranged concentrically on the inside and outside in the radial direction, so that the in-plane uniformity of the processing characteristics is maintained. Furthermore, by implementing dual-frequency ICP, it is possible to achieve both the in-plane uniformity of cycle etching and the etching performance of dual-frequency ICP.

In a deposition evaluation using a 13.56 MHz power distributor and SiF ₄ /O ₂ gas, it was confirmed that the in-plane deposition distribution can be changed by changing the distribution from IN:OUT = 999:0 to 0:999 (corresponding to a distribution ratio of 0.9:0.1 to 0.1 to 0.9). Similarly, in an etching evaluation using SF ₆ /SiF ₄ /O ₂ , it was confirmed that although the in-plane distribution fluctuated, the amount of fluctuation was small.

In a film formation evaluation using _SiF4 / _O2 gas in a dual frequency superposition using 13.56 MHz and 2 MHz, the tendency of center fast did not change compared to 13.56 MHz alone (corresponding to IN:OUT = 999:0 when a power splitter is used), but in an etching evaluation, it was confirmed that there was a large impact that caused a change from center fast to edge fast.

Similarly, in the evaluation of the deposition of a film using _C4F8 gas in a dual frequency superposition using _13.56MHz and 2MHz, the deposition distribution changes significantly depending on the position of the gas inlet (center, periphery), but in the evaluation of the deposition of a film using _SiF4 / _O2 gas, no difference due to the position of the inlet was observed. Therefore, it was possible to conclude that this change was due to the influence of 13.56MHz.

From the above, it was found that if 13.56 MHz is introduced to the two inner and outer antennas at the desired distribution ratio using a power divider, it is possible to align the in-plane distribution of cycle etching by controlling the etching distribution of _SF6 / _SiF4 / _O2 and the film formation distribution by _SiF4 / _O2 .

Here, in the past, in a conventional dual-frequency ICP antenna with 13.56 MHz and 2 MHz positions, in cyclic etching in which film formation and etching are alternately repeated, the difference in distribution at each step could not be improved, and the in-plane distribution of the etching shape after the process was not controllable.
That is, in the cycle etching, a gas whose characteristic distribution is particularly strongly influenced by the spatial distribution of the 13.56 MHz plasma is used in the deposition process, and a gas whose characteristic distribution is influenced by the spatial distribution of both the 2 MHz and 13.56 MHz plasma is used in the etching process. Moreover, these processes must be repeated.

In this way, when deposition and etching processes are performed alternately, even if one distribution is good, it is difficult to maintain the in-plane uniformity of the processed shape unless the other distribution is the same. However, with plasma processing equipment equipped only with conventional antennas, the antenna shape is fixed and the spatial distribution of the magnetic field it creates cannot be changed, making it difficult to improve the in-plane distribution of the processing characteristics for each individual process.

In the Dual TSV Process (Cycle Etching), the film formation process using SiF ₄ /O ₂ gas is essential to protect the resist film. It is known that the film thickness distribution in this film formation process depends on the spatial distribution of plasma. In the conventional dual-frequency ICP antenna, the plasma spatial distribution is fixed, so the process distribution cannot be controlled.
In order to solve this problem, the present invention has realized a plasma source that allows spatial distribution control of dual-frequency ICP by using power distribution technology and dual-frequency ICP. This allows the distribution of Depo1 film (SiF ₄ /O ₂ gas) and etching (SF ₆ /SiF ₄ /O ₂ gas) to be matched, improving the processing uniformity within the wafer surface. It can be confirmed that the film thickness distribution changes by adjusting the distribution ratio by the power distributor, and by controlling this power distributor, it is possible to match the etching surface distribution formed by 2MHz + 13.56MHz.

In the resist protective film formation step (deposition process using SiF ₄ /O ₂ gas) in the cyclic etching process, it is preferable to set the power distribution ratio between the inside and outside of the antenna to be inside:outside=0.5:0.5 to 0.1:0.9.
In the sidewall protective film forming step (deposition process using C ₄ F ₈ gas) in the cyclic etching process, it is preferable to set the power distribution ratio between the inside and outside of the antenna to be inside:outside=0.75:0.25 to 0.25:0.75.
In the etching step (dry etching process using SF ₆ /SiF ₄ /O ₂ gas) in the cyclic etching process, it is preferable to set the power distribution ratio between the inside and outside of the antenna to be inside:outer=0.75:0.25 to 0.25:0.75.

Furthermore, an electrode (antenna) to which a second frequency λ2 for heating plasma is applied can be provided radially inward of the first electrode E1.
Furthermore, an electrode (antenna) to which a second frequency λ2 for heating plasma is applied can be provided radially outside the second electrode E2.
Furthermore, these arrangements may be combined.

Alternatively, the first electrode E1, the second electrode E2, and the third electrode E3 may have a structure of one to three stages in the height direction on the same axis.
These features enable efficient heating of the plasma, and also enable efficient control of the spatial distribution of the plasma in processing a large-area substrate.
Furthermore, these configurations can be taken out individually and arbitrarily combined to form an arrangement.

An example of how this invention can be used is the silicon through-hole formation process in semiconductor manufacturing.

10: Plasma processing apparatus 11: Chamber 12: Internal electrode (support means)
13: Upper cover 15: Gas inlet 100: Gas introduction means G: Process gas S: Object to be processed (substrate)
TMP: exhaust means (pressure reducing means)
17...First high frequency power source (plasma generating power source)
18...Second high frequency power source (plasma heating power source)
19...High frequency power source (third high frequency power source)
E1...first electrode (antenna AT1)
E2: second electrode (antenna AT2)
E3: third electrode (antenna AT3)
G: Process gas M/B: Matching box

Claims (12)

A plasma processing apparatus comprising:
A chamber capable of reducing the pressure inside and configured to perform plasma processing on a workpiece inside the chamber;
a flat inner electrode disposed in the chamber and on which the workpiece is placed;
a spiral external electrode disposed outside the chamber and facing the internal electrode across a dielectric plate forming an upper lid of the chamber;
A plasma generating power source that applies AC power of a predetermined frequency to the external electrode;
a gas introduction means for introducing a process gas into the chamber;
Equipped with
the external electrode is divided in a radial direction to include a first spiral electrode arranged on a radially central side, a second spiral electrode arranged on a radially outer periphery, and a third spiral electrode arranged to be sandwiched between the first electrode and the second electrode in the radial direction,
The plasma generating power source is
a first high frequency power supply that applies AC power having a first frequency λ1 to the first electrode and the second electrode;
a second high frequency power supply that applies AC power of a second frequency λ2, the second frequency λ2 having a relationship of λ1>λ2 with the first frequency λ1 to the third electrode;
a power distributor that distributes power so that AC power distributed at a predetermined distribution ratio can be applied to the first electrode and the second electrode;
Equipped with
2. A plasma processing apparatus comprising: A plasma having a adjusted spatial distribution is generated by AC power of the first frequency λ1 distributed and applied to the first electrode and the second electrode, and an electron density of the plasma is increased by AC power of the second frequency λ2 applied to the third electrode.
2. The plasma processing apparatus according to claim 1, the power distributor is capable of distributing and applying a power at a predetermined distribution ratio such that a magnetic field distribution formed by the first electrode and the second electrode substantially coincides with a magnetic field distribution formed by the third electrode.
2. The plasma processing apparatus according to claim 1, The first high frequency power supply and the second high frequency power supply apply AC power having the first frequency λ1 of 13.56 MHz to the first electrode and the second electrode, and apply AC power having the second frequency λ2 of 2 MHz to the third electrode.
2. The plasma processing apparatus according to claim 1, The external electrode has portions stacked in the axial direction of the spiral.
2. The plasma processing apparatus according to claim 1, A method for performing plasma processing using the plasma processing apparatus according to any one of claims 1 to 5, comprising the steps of:
A plasma is generated by the first electrode and the second electrode to which AC power of the first frequency λ1 is applied by the first high frequency power supply, and the AC power of the first frequency λ1 to be applied is distributed to the first electrode and the second electrode at a predetermined distribution ratio by the power distributor, thereby adjusting the spatial distribution of the generated plasma;
Increasing the electron density of the plasma by the third electrode to which AC power of the second frequency λ2 is applied by the second high frequency power supply;
1. A plasma processing method comprising: a distribution ratio of AC power applied to the first electrode and the second electrode by the power distributor is changed in response to the process gas introduced by the gas introduction means, thereby adjusting the spatial distribution of the generated plasma.
7. The plasma processing method according to claim 6. The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.5:0.5 to 0.1:0.9
Set it to be in the range of
8. The plasma processing method according to claim 7. The process gas is a film formation process using SiF ₄ /O ₂ gas;
9. The plasma processing method according to claim 8. A distribution ratio of AC power Winner distributed to the first electrode and AC power Wouter distributed to the second electrode by the first high frequency power supply is
Winner:Wouter = 0.75:0.25 to 0.25:0.75
Set it to be in the range of
7. The plasma processing method according to claim 6. The process gas is _{C4F8 gas} for film formation;
The process gas is SF ₆ /SiF ₄ /O ₂ gas etching process;
11. The plasma processing method according to claim 10. The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.5:0.5 to 0.1:0.9
The process gas is set to be in the range of SiF ₄ /O ₂ gas for film formation,
The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.75:0.25 to 0.25:0.75
The process gas is set to be in the range of C ₄ F ₈ gas for film formation,
The power distributor divides the AC power Winner distributed to the first electrode and the AC power Wouter distributed to the second electrode into a distribution ratio of:
Winner:Wouter = 0.75:0.25 to 0.25:0.75
The process gas is set to be in the range of SF ₆ /SiF ₄ /O ₂ gas for etching;
This is done continuously without breaking the vacuum.
7. The plasma processing method according to claim 6.

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